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3rd Party List
A list purchased, rented, or somehow obtained from an outside company. The email addresses on the list have not specifically signed up to receive mail from your company, but have opted in through the other company to receive mail.

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A Record
An A Record, short for Address Record, maps from an IP address to a domain name. An A record is also referred to as a host or hostname.
AAAA Record
The AAAA resource record type is a record specific to the Internet class that stores a single IPv6 address.
The Access Control List, which on the Managed DNS system is a set of permissions for determining who may edit what for a given zone. Each zone has its own ACL and all zones are created with a default ACL to facilitate maximum usability. Account owners and admins may edit the ACL for a zone if they wish to place restrictions on user activity for the zone.
Active Failover
Active Failover enables your website to stay up and running – all while making the experience a seamless one for your visitors. When an outage is detected, your traffic is automatically re-routed to an alternate endpoint that you have preconfigured.
Admin is a user Role within Managed DNS. Admins have the second-highest level of access, being able to create zones, add services to zones and edit ACLs.
Alt Tags
Alt tags provide alternative text on an image that is displayed if the email client is set to not display images or if a slow connection has delayed the load of an image.
Data to be included in a DNS query response. Must include a record type (A, AAAA, CNAME, SRV, etc.), but (in the context of Dynamic Steering) does not need to include an associated domain name or specific TTL or CLASS.
An Application Program Interface is a set of rules established by an application or system for communicating with it. Managed DNS and Email Delivery provide an API for use with end user programs.
DNS network topology that uses BGP to route DNS queries to the fastest nameserver on the network.
An ASN (Autonomous System Number) is a unique identifier for a network of routing prefixes.
A network resource owned by (or of interest to) one or more customers, such as a subnet (including an individual address), domain name, autonomous system number (ASN), CDN, cloud provider region/zone, or origin.
Attached Domains
A FQDN with an established relationship with a Dynamic Steering Policy.
Auth Code
The auth code (sometimes called an EPP code or a transfer code) is a string, usually between 8 and 16 characters long and randomly created at the time of a domain’s registration, used to authorize transfers in certain Top Level Domains. The auth code provides an extra layer of security over the normal transfer request procedures.
Authentication lets IPSs and mailbox providers know that the emails you are sending are approved to be sent by the domain they are coming from and are not spam or phishing emails.
Authoritative Nameserver
A nameserver which has been configured to provide answers for a specific domain, rather than simply getting and caching data about domains from other nameservers.

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BGP (Border Gateway Protocol) is the protocol used in the operation of the Internet to move data between autonomous systems.
Billing is a user Role within Managed DNS. Billing users have no access to edit any zone data, but do have full rights to the billing information of the account. They can create and authorize payments and generally handle the financial side of the account.
BIND (Berkeley Internet Name Domain) is an implementation of the DNS protocol. The BIND DNS server is used on the vast majority of Internet name servers, and is the reference implementation of the DNS specification.
Blacklists help keep the Internet clear of unsolicited email by giving mail providers a list of offending email senders (spam) that they can automatically block and keep away from inboxes.
Emails which were sent but not delivered to the recipient. There are several types of bounced Email: Hard Bounce, Soft Bounce, Suppressed, Previously Hard Bounced, and Previously Complained.
Bulk Mail
Commercial mail sent out by companies. Any email marketing campaign is bulk mail (newsletters, promotions, coupons, etc.). Bulk mail sends out to the entire list at once.

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Caching refers to a process where DNS servers store copies of information they get from other DNS servers, so they don’t have to ask the same question over and over. The amount of time something is cached is determined by the TTL on the record.
Controlling the Assault of Non-Solicited Pornography and Marketing Act (CAN-SPAM) was a law passed in the United States in 2003 to set standards on sending email.
A Content Delivery Network is a network of servers that serves content to end users from the closest node for the fastest load time.
CIDR (Classless Inter-Domain Routing Notification) is a standard syntax for specifying IP addresses and their associated routing prefix. The routing prefix is shown as an appended slash character and the decimal number of the leading bits of the routing prefix. IPv4 example:; IPv6 example: 2001:db8::/32
When an email recipient clicks on a link within an email message. Unique clicks only count one click per user, meaning that if one recipient clicked a link multiple times, only their initial click is counted.
Update clients are small applications that run on your system and are used to automatically update your hostname when your IP address changes. For Dynamic Steering, a client is a source of queries (DNS, HTTP, etc.).
A CNAME is a special type of DNS record used to create an alias from one hostname to another. For example, if we say “www.yourdomain.com is a CNAME to yourdomain.com” that means that someone accessing www.yourdomain.com will be pointed to the same IP address that yourdomain.com points to. This is useful so that, when your IP address changes, you only have to update yourdomain.com’s entry, and www.yourdomain.com automatically points to the right place.
When an email recipient hits the spam button in their inbox, an email provider’s spam filtering will often record this as a complaint and prevent future email from that sender from reaching the inbox. Some email providers will provide a feedback loop of complaints, so that senders can be informed and keep their lists clean. Complaints should be kept as low as possible. Otherwise, the IP address may be blacklisted.
Content Filters
Spam filters that review the content of an email to attempt to make a decision on whether that email should go to the spam folder or inbox. These systems are often reviewing things such as keywords, text-to-image ratio, templates, and other content based items.
Cut Node
Cut nodes allow you to keep the DNS for your zone with your current DNS provider, but point or cut a specific node over to Dyn’s nameservers, allowing you to use one of our advanced features.

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Data Center
Data centers house servers, computer systems, and other telecommunication components, usually with redundant power and special security measures. They are designed to withstand major natural and man-made disasters.
Distributed Denial of Service is an attack when multiple systems are used to flood servers with traffic in an attempt to overwhelm its available resources (bandwidth, memory, processing power, etc), making it unavailable to respond to legitimate users.
Dedicated IP Pool
A dedicated IP pool is when an email sender is the only company, sender, or domain to utilize that IP or set of IPs for sending email.
To specify in DNS which nameservers handle a specific domain/subdomain. See also delegation.
Delegation, as a verb (see also delegate), is the process of designating the nameservers for a domain. As a noun, it is used to refer to the current set of nameservers to which a domain has been delegated.
The measurement of a message’s ability to successfully be delivered to the intended recipient. Inbox deliverability refers to the amount of actual inboxes that the message reached, excluding delivery to junk folders.
Domain Keys Identified Mail is an email authentication framework system that allows mailbox providers to validate mail from your domain against a public (DNS) and private (embedded within the email) key, thus validating mail from your domain, protecting your brand and customers.
Domain-based Message Authentication, Reporting & Conformance is a standardization that uses SPF & DKIM to authenticate email sends in order to help eliminate phishing emails.
DNS (the Domain Name System) provides mapping of hostnames to IP addresses and back again.
DNS Client
Also known as a DNS resolver, a DNS client is the system that makes a DNS request (e.g. your computer, smart phone, an ATM).
DNS Query
A request a client sends to a DNS server to resolve the IP address for a domain name or hostname.
DNSSEC is the act of adding special signatures to the root, TLD, and authoritative nameservers for your zone to establish a chain of trust. DNSSEC enabled zones ensure that the answer to a DNS query has not been tampered with.
A DNS-based Blackhole List, or DNSBL, is a means by which an Internet site may publish a list of IP addresses, in a format which can be easily queried by computer programs on the Internet. As the name suggests, the technology is built on top of the Internet DNS or Domain Name System. DNSBLs are chiefly used to publish lists of addresses linked to spamming. Most mail transport agent (mail server) software can be configured to reject or flag messages which have been sent from a site listed on one or more such lists. (This definition from Wikipedia.)
A Denial of Service is an attack on a URL that is coming from one source.
A domain, or domain name, is what identifies a group of computers on the Internet. An example would be dyndns.org, which is the domain for many computers that use our service, where the name of a particular computer (in this case, the web server) would be www. In other words, the full name of the computer is www.dyndns.org. A domain name is fully qualified when it is a complete hostname, e.g. “hostname.homeip.net” instead of simply “hostname.”
Double Opt In List
Recipients that are double-opted in have gone through an initial signup (first opt-in) and then received an email in which they take a second action (second opt-in), most often by clicking a link where their intent to opt-in to your email list is confirmed.
In an IP Address context, dynamic means changing, usually quite often. Dynamic in this context is the opposite of static.
Dynamic DNS
DDNS is a term used to describe services that alias a dynamic IP Address to a static hostname. This is the type of service we began by offering, and we plan to continue offering. Many ISPs charge, some up to $200/month, just for a static IP address. We emulate this ability for little or no charge.
DynScore is a business logic system that provides deliverability insight, and actionable advice based on your email delivery metrics. Users can monitor their DynScore, implement the suggested corrective actions and watch their DynScore trend upward, ultimately providing better deliverability.

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The Sent (Email) count includes all pieces of mail processed through the Email Delivery system. It is used for billing purposes.
The Delivered (Email) count is the measure of all Sent Email less the total of Bounces, List Unsubscribes, Complaints, and Sending Issues.
Engagement refers to how recipients of email interact with messages they receive. An engaged user opens the email, reads it, and maybe clicks a few links. An unengaged user either never opens a message, or quickly closes or deletes it after opening.
The end location, or target, of a DNS client – IP address or CNAME. For DII, the start or end of a specific path through the Internet.
Email Service Provider (ESP) refers to the company that provides the capabilities for end users to send email.

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When your primary server goes down, failover is the act of rerouting traffic to a redundant server. (Also see Active Failover.)
Forward Lookup
A forward lookup is when you use a hostname (domain name) to find an IP address. Find out your IP address: http://checkip.dyn.com/
FTP server
FTP stands for File Transfer Protocol. An FTP server is simply a file server, a simple way for people to access files on a particular computer from any other computer with Internet access.
Feedback Loops
Feedback loops are channels of communication between mailbox providers and email senders that allows those providers to communicate any message that was identified as spam by a recipient. These need to be manually established at each mailbox provider that allows for feedback loops.
Fully Qualified Domain Name
A fully qualified domain name is a complete hostname, like that which you would use when connecting to a server on the Internet. Fully qualified hostname must be used when updating with a client, e.g., if your hostname is “myhost.dnsalias.net”, you must provide that entire hostname to the client, not simply “myhost.”

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Global Server Load Balancing responds to DNS requests by directing traffic with the best performing server in a geographic region.
gTLD Servers
The gTLD servers are a set of nameservers which contain information about all domains in the com, net, and org top-level domains.

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Hard Bounce
Hard bounces occur when a mailbox provider provides a signal that the email address you have tried to send to is not valid. Most often, this happens because the email address does not exist. You should not try to email this address again in the future.
One stop along a path through the Internet, defined by one router, one provider, and one location.
A hostname (also referred to as a “host”), is a computer’s unique name on the Internet, which points to that computer’s IP address.

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Internet Control Message Protocol (ICMP) is the protocol used by network devices, such as routers, to send error messages indicating that a requested service, host, or router is unavailable or cannot be reached. When traceroutes are run, the ICMP option supplies responses to the sender from all of the routers traversed.
IP Address
An IP address is how computers all over the Internet find each other. It is similar to your street address, except it is for computers. IPv4 addresses look something like IPv6 addresses look something like fe80::216:3eff:fe1e:c440. They are often hard to remember numbers, and they certainly don’t tell you very much about a computer. That is why we provide aliasing services. IP addresses can be static or dynamic.
Internet Service Providers are those providing their customers access to the Internet. They are also commonly mailbox providers (e.g. Comcast, AT&T, Verizon).
Iterative Query
An iterative query commonly takes place when a name server gives another name server the best answer it has for an IP query. An example of which is when a server asks root the location of example.com, the root responds with the best answer it can to the .com nameserver.

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KEY Resource Record
The KEY Resource Record stores a public key associated with a DNS name.

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The round-trip time to move information from one point on the Internet to another. It includes the time for information to travel through fiber as well as that required for processing (switching). Latency is also used to describe the length of a delay that end users experience when trying to access content.
List Maintenance
Monitoring the health of an Email list by removing hard bounces, people who unsubscribe, and possibly creating suppression lists for unengaged users. List maintenance is crucial for keeping a good sender reputation and deliverability high.
Load Balancing
Load Balancing is used to distribute your traffic over several servers, resulting in increased reliability and efficiency.
LOC Resource Records
LOC Resource Records allows for adding location information to your zone file. Data in a LOC Record includes the latitude, longitude and altitude of the host, network or subnet with which it is associated.

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Mailbox Provider
A mailbox provider, commonly also ISPs, are those that provide end recipients mailboxes to receive and send email. Common mailbox providers are Yahoo!, Gmail, AOL and Hotmail.
Mail eXchanger (MX)
A Mail eXchanger is a type of DNS record that allows you to control the delivery of mail for a given domain or subdomain. In our context, MX records can be set on a host-by-host basis to point to other hosts on the Internet (usually with permanent connections) that are set up to accept and/or route mail for your hostname(s). Setting a Backup MX makes the entry you specify a secondary mail exchanger. This means that delivery will be attempted to your host first, and then to the backup host you specify if that fails.
Multiprotocol Label Switching (MPLS) is the method used by telecommunication networks to direct data from one network node to another based on short path labels rather than long network addresses. MPLS “tunnels” are used to efficiently transport traffic between hubs.
The Message Transfer Agent is a software application that transfers and routes email from sender to recipient.

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A nameserver is a server which has been set up to answer DNS queries, and provide information about a certain set of domains.
A Node in our context is a DNS label. The parts of a domain between the dots. A Node can also refer to a Subdomain.
NS Resource Records
NS Resource Records designate which nameserver(s) are responsible for answering DNS queries for a domain or subdomain.

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When a recipient of an email clicks an email message in their inbox to see the body of the message. Unique opens excludes the multiple number of times a single recipient may open a message.
An address or hostname asset capable of responding to client requests in a particular protocol (e.g., HTTP or—distinctly—HTTPS) for customers.
Owner is a user Role within Managed DNS. Owners have the highest level of access, being able to create users and zones, add services to zones and edit ACLs.

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Any provider involved in a business relationship to handle Internet traffic through a peering arrangement.
A business relationship between ISPs to exchange traffic between their customers, generally at no cost. These agreements reduce costs and improve performance.
Phishing is when an ill-intentioned party tries to gain sensitive information like passwords or credit card information by falsely appearing as a trusted brand. A common phishing ploy is when phishers masque themselves as banks to gain account information.
In the context of Dynamic Steering, a configuration specifying answers and rules for when to include them in DNS response messages.
A Point of Presence is the physical location of a server, data center, etc.
Postback URLs
When activated, any time an email is bounced or spam complaint is received, these URLs are activated to execute any custom script on your servers you would like.
A collection of IP addresses, written in the form a.b.c.d/e, where e is a measure of how many IPs are contained within the prefix.
Primary DNS
The DNS provider with control of zone file modification.
PTR Records
PTR records are a reverse lookup for an A record. Due to the nature of DNS and the way reverse lookups work, PTR records can only be controlled by your ISP.

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Queries per Second (QPS) is the measurement used in DNS to record how many queries a DNS server is receiving.
Queries per Month (QPM) is a measurement used in DNS to record how many queries a DNS server is receiving.
When a computer or networked device makes an inquiry to retrieve an IP address, or other resource record information, from a domain.

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Readonly is a user Role within Managed DNS. As expected, Readonly users have a low level of access, being able to only view zones and other account information by default. This role is useful for people who may need to look at the zone data or contact information but never make any changes to it.
Resource records are basic information elements of the Domain Name System (DNS). There are many types of records and the information they can contain is based on the record type.
Recursive Query
A recursive query takes place when a DNS client makes a request to the recursive server for the IP address of a hostname. The recursive server will either return the answer or an error message that the domain does not exist.
Recursive Resolver
The recursive server is typically supplied by your ISP and is the server where a DNS client makes its initial query. Once the recursive server receives the correct information about an IP address from other nameservers, the recursive server will cache the information.
Redundancy is having more than one server available. In the situation of a failure, a redundant server can be used as a backup.
Your registrar is the organization through whom you’ve registered your domain. Dyn, for example, is a registrar for com/net/org domains (and some others).
Rented or bought refers to lists of email addresses that have been created by 3rd parties that your company pays for to acquire a large list of email addresses.
Sender Reputation is how ISPs view your email sending habits. A good reputation consists of low bounce rates and low complaints.
A web object served by all origins within a scope, used by Dyn’s Dynamic Steering to monitor their health and performance.
Reverse Lookup
Looking up an IP address to retrieve a host name.
Each user on the Managed DNS system has a Role. The supported roles are: Owner, Admin, Tech, Billing, Update and Readonly. Roles determine the basic level of access to the account and the Managed DNS system. Account owners will create users with a role corresponding to the level of access they wish to allow. Roles also come into play with the ACL system for zone editing.
Root Servers
The root servers are nameservers that all other nameservers on the Internet know about, and contain very basic information about the DNS system, which will lead other servers along the path to finding out specific information about a host.
Round Robin
Distribute server load evenly across multiple servers.
A device that directs traffic between two or more networks or network sections.
Real Time Traffic Management monitors all of your endpoints to detect the best-performing one and provides you with the lowest latency possible. RTTM collects real-time data to track the load time of each of your endpoints, rather than just routing your traffic to the closest geographical data center.
Used to identify specific metrics that qualify policy answers in Dynamic Steering. Availability Rules identify policy answers based on whether the identified resource registers as ‘up’ or ‘down’. Performance Rules identify policy answers based on latency and packet loss measurements from a predefined collector set. Max Count Rules define the maximum number of answers the customer would like served in the response.

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A domain of interest for Dynamic Steering, used to separate relevant data from the whole haystack.
Secondary DNS
Secondary DNS provides backup DNS servers that download information from your primary DNS server and share its load. Secondary DNS servers essentially have a read-only copy of the zone that stays in sync with the master or primary DNS server.
The process of sending your email messages to previously defined Dyn owned sample accounts, called Seed Accounts, for the purpose of determining your deliverability. It is possible to resolve many customer issues by viewing the actual performance of an email message delivery.
Sender ID
Sender ID is a way to validate that emails are being sent by verified domains. It does this by verifying the IP address that the messages are being sent from, checking them against the records for the owner of the domain.
Shared IP Pool
A shared IP pool is an IP address that multiple senders may send from. Generally, senders with smaller sending habits share an IP address.
Simple Mail Transfer Protocol is used to send and receive email.
SOA Resource Records
The Start Of Authority record is required for each zone. It contains the name of the zone, the e-mail address of the person responsible for administering the domain’s zone file, the current serial number of the zone, the primary nameserver of the zone, and various timing elements (measured in seconds). Entering SOA data is one of the methods for creating a zone in Managed DNS.
Soft Bounce
Soft bounces are messages from a mailbox provider that provide a signal that the email address you have tried to send to is not valid for the time being. Usually a message soft bounces when the inbox is currently full or cannot be reached. You may try to email this address again in the future.
SOAP Interface
The Simple Object Access Protocol is an XML based protocol that acts as an intermediary layer for communicating over the web. Managed DNS provides a SOAP based API for users to manage their data.
Spam is any Email message received that is not wanted by the recipient. Spam is often thought of as messages about schemes or health supplements, among many other unwanted messages.
Spam Trap
Spam traps are email addresses that are placed on websites and not opted into any email list for the purpose of finding spammers that gather lists of email addresses to try to market to. Sending any email to these spam traps can cause your IPs or Domain Names to be blacklisted, heavily impacting your deliverability.
Sender Policy Framework is an email validation system that allows mailbox providers to validate mail from your domain against the IP Address sending the mail. If a mail server doesn’t appear in a domain’s SPF record, but is attempting to send mail from that domain, it is most likely spoofed or unapproved mail and can be rejected by the ISP.
Spoofing is the act of making an email address look like a different sender than the actual sender. Spammers use spoofing to get by spam filters by sending mail through a more reputable “From” address.
SRV Resource Records
SRV Resource Records are a generalized way to specify which hosts in a domain respond to various services on a given protocol and port. Support for SRV records is still very limited across the Internet.
Static means unchanging, not moving. In the context of an IP Address, it means that the address stays the same each time that you logon or connect to the Internet. Most static IP addresses are on permanent connections, that stay on the Internet all the time, but some are on home dialup connections. In an IP context, the opposite of dynamic.
A subdomain is somewhere in-between a domain name and a hostname. A subdomain adds another level to a domain; an example would be is.mine.nu, a subdomain of mine.nu.
A suppression list contains email addresses that are not to be sent to. Commonly, unsubscribed email addresses are placed into a suppression list so that they will not receive future messages.

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Tech is a user Role within Managed DNS. Techs have a medium level of access, being able to edit zones, create contacts and view other data.
Text-to-Image Ratio
The ratio of text-to-image space in an email. Having too many images or too large of an image in an email can cause the spam weight of the email message to go up, causing it to go to the spam folder.
Top Level Domain – .com, .net, .org, etc.
Traffic Director
An advanced service for Dyn’s Managed DNS that integrates geographic load balancing with monitoring and failover features.
Traffic Management
Traffic Management is an advanced feature that allows for the weighted distribution of application load between global data centers, cloud providers, or your existing CDNs based on seven geographic regions. This gives customers the flexibility to route traffic in each region to the optimal endpoints in their infrastructure.
A tool for measuring the specific path followed from a starting IP address to an ending IP Address, involving one or more router hops and returning the latencies. The term is also used for the collected information.
Transactional Mail
Transactional Mail is any message sent that was triggered by an action from the recipient. Examples are commonly receipts, but can also be account notifications, shipping notifications, password resends, etc.
TTL is the amount of time in seconds that a DNS record will be cached by an outside DNS server.
TXT Records
TXT records are used to store information. Common uses include SPF, DKIM, etc.

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In a Unicast network, there is only one responding DNS server.
Update is a user Role within Managed DNS (also called Updaters), it is exclusive with other roles. Updaters have a minimal level of access, only being able to update dynamic A and AAAA records by default. Updaters may not login to the WBZE. They are intended to be the login credentials for the dynamic update clients.
Uptime and Downtime refer to if a server is currently active or is unavailable, respectively.
When an email recipient of your message requests to be removed from any future communication, this is called unsubscribing. Unsubscribes do not negatively affect your sender reputation.
A Uniform Resource Locator, or URL, is used as a standard way of specifying the location of a web page or other object on the internet. URLs often appear on web pages as links to other sites.

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Vantage Point Collectors
Also called “Collectors”, these stations around the world gather information from BGP announcements and run traceroutes to over 1.5 million targets throughout each day. The data collected populates the DII reports of latencies, paths, and network connectivity maps.

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Warming IP
When senders first start sending mail, they must warm up the IP address they are using so that they can be deemed as a reputable sender. The process happens slowly over time by sending out a low volume of messages and then building up over time.
A collection of endpoint pairs containing one vantage point (first endpoint) and one market city and provider (second endpoint). Daily median latencies are recorded for each endpoint pair and daily changes are presented on the watchlist.
The Web Based Zone Editor is Managed DNS main interface for managing your hosted zone. You can learn more about the WBZE and how to use it in our User Guide.
A list of senders that recipients have deemed acceptable to receive mail from.

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Non-standard Email header items that can be customized and sent along with email messages to retain specific details that are important to the sender, ESP, ISP, or the recipient. These can be used to tag, categorize and segment email in Dyn’s Email Delivery.

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A portion of the DNS namespace that has been divided up for more granular administration of DNS. Zones hold DNS records that contain mapping information.