How to build an email allow list using MX records for initial email validation?

Summary

Building an email allow list using MX records involves classifying domains based on their MX records, identifying known MX patterns for major providers (e.g., AOL, Outlook, Microsoft, Yahoo), and caching these records for faster validation due to their relative stability. MX records, found in DNS settings, specify mail servers responsible for accepting emails and include priority numbers; lower numbers are tried first. Continuous monitoring and updates are essential for maintaining an accurate allow list. Feedback loops can also improve whitelisting effectiveness by providing insights into audience engagement.

Key findings

  • MX Record Classification: Classifying domains by their MX records aids in building allow lists.
  • MX Record Stability: MX records are relatively stable, making caching a viable strategy.
  • MX Record Examples: Specific MX record patterns identify major email providers.
  • DNS Settings: MX records reside in DNS settings provided by the domain host.
  • MX Priority: MX records have a priority; lower numbers are attempted first.

Key considerations

  • Continuous Monitoring: Regular updates and monitoring are necessary to maintain allow list accuracy.
  • Feedback Loops: Utilizing feedback loops can enhance whitelisting effectiveness.
  • DNS Access: Access to DNS settings is needed to modify or check MX records.

What email marketers say
11Marketer opinions

Building an email allow list using MX records involves querying MX records to identify known good domains and caching those results for quick validation of new sign-ups. This includes checking domains against known MX records of major providers like Microsoft and Yahoo. Verifying that a domain has valid MX records is a basic step in ensuring deliverability, as MX records point to the mail servers responsible for accepting email messages on behalf of a domain. Also note MX records can point to subdomains as well as the primary domain, allowing for flexible email routing configurations.

Key opinions

  • MX Record Validation: MX record verification is a fundamental step in ensuring email deliverability.
  • Caching MX Records: Caching MX records of known good domains enables faster validation processes.
  • Identify Major Providers: Checking MX records against known MX records of major providers like Microsoft and Yahoo is helpful.
  • MX record flexibility: MX records can point to subdomains as well as the primary domain.

Key considerations

  • Continuous Monitoring: Allow lists require continuous monitoring and updates due to dynamic domain configurations.
  • Deliverability Impact: Validating MX records is a basic step for email deliverability.
  • MX Records Role: MX records indicate which mail servers are responsible for accepting emails.
Marketer view

Email marketer from SparkPost explains that MX records point to the mail servers responsible for accepting email messages on behalf of a domain. Verifying that a domain has valid MX records is a basic step in ensuring deliverability.

April 2021 - SparkPost
Marketer view

Email marketer from Email Hippo shares using MX records in email verification helps determine whether a domain accepts email, and this, is one factor, in determining whether an email address is likely to be valid and active.

March 2021 - Email Hippo
Marketer view

Email marketer from Reddit suggests querying MX records to identify known good domains and cache those results. This allows you to quickly validate new sign-ups against a known list of trusted email providers like Gmail or Outlook.

July 2024 - Reddit
Marketer view

Marketer from Email Geeks suggests checking a domain against known Microsoft MX records to identify O365 domains and caching the results.

August 2021 - Email Geeks
Marketer view

Email marketer from GlockApps explains that an MX record is a type of DNS record that directs email to the correct mail server. It includes the priority and hostname of the server that handles incoming mail for a domain.

February 2023 - GlockApps
Marketer view

Marketer from Email Geeks advises that it’s easier to check domains against a set of Yahoo MX servers than to maintain a list of all Yahoo domains.

March 2021 - Email Geeks
Marketer view

Email marketer from Namecheap explains how to add your email address to an allowlist. They say to add your sending email address to the safe sender's list, or the contact list. Doing this helps prevent your legitimate emails from being filtered as spam.

October 2021 - Namecheap
Marketer view

Email marketer from StackOverflow shares that you can extract the domain name from an email address, perform an MX record lookup, and compare the retrieved MX records against a known list of legitimate providers. If the MX record matches, the domain is likely valid.

October 2021 - StackOverflow
Marketer view

Marketer from Email Geeks suggests digging the MX records on a domain when a signup comes in, pooling by the collection of those MX records, caching once you see things, and refreshing on occasion.

September 2022 - Email Geeks
Marketer view

Email marketer from EasyDMARC shares that MX records are essential because they tell other mail servers where to send email for your domain, enabling proper email delivery and reception.

September 2021 - EasyDMARC
Marketer view

Email marketer from DNS Records notes MX records can point to subdomains as well as the primary domain, allowing for flexible email routing configurations.

August 2023 - DNS Records

What the experts say
6Expert opinions

Building an email allow list using MX records involves classifying domains based on their MX records and adding domains with known MX patterns to the allow list. Caching MX records is possible since they don't change frequently. Examples of MX records include mx-aol.mail.gm0.yahoodns.net for AOL and outlook-com.olc.protection.outlook.com for Outlook. Maintaining an accurate allow list requires continuous monitoring, and feedback loops can provide insights into audience engagement to improve whitelisting.

Key opinions

  • MX Record Classification: Classifying domains by MX records is a method for building allow lists.
  • MX Record Stability: MX records are relatively stable and suitable for caching.
  • MX Record Examples: Known MX patterns identify major providers (e.g., AOL, Outlook).

Key considerations

  • Continuous Monitoring: Maintaining an accurate allow list necessitates continuous monitoring and updates.
  • Feedback Loops: Feedback loops can improve whitelisting effectiveness by providing audience insights.
Expert view

Expert from Spam Resource explains that maintaining a current and accurate allow list based on MX records involves continuous monitoring and updates due to the dynamic nature of domain configurations.

February 2023 - Spam Resource
Expert view

Expert from Email Geeks provides examples of MX records, like mx-aol.mail.gm0.yahoodns.net for AOL and outlook-com.olc.protection.outlook.com for Outlook.

September 2023 - Email Geeks
Expert view

Expert from Email Geeks notes that MX records don’t change that often, so you can often cache for a while.

February 2024 - Email Geeks
Expert view

Expert from Email Geeks explains that you should classify domains by their MX records; if it’s a known MX pattern, add it to the allow list.

September 2021 - Email Geeks
Expert view

Expert from Email Geeks says you can look up and cache MX records as they don’t change that often.

April 2023 - Email Geeks
Expert view

Expert from Word to the Wise says that feedback loops can assist in the process of whitelisting as it allows the sender to have a better understanding of their audience and how they engage with messages. These are often free to set up.

January 2022 - Word to the Wise

What the documentation says
5Technical articles

Building an email allow list requires understanding MX records, which are found in DNS settings. These records specify the mail server for a domain and include a preference number; lower numbers are tried first. You can add/modify these in domain control panels, with considerations for TTL: low TTL for faster propagation and high TTL for less frequent lookups. MX records specify the mail server responsible for accepting emails for a domain, including a preference value.

Key findings

  • MX Record Location: MX records are located in DNS settings at your domain host.
  • MX Record Priority: MX records have priority numbers; lower numbers are tried first.
  • MX Definition: MX records specify mail servers for accepting emails on behalf of a domain.

Key considerations

  • DNS Configuration: Adding and modifying MX records requires accessing your DNS control panel.
  • TTL Setting: The TTL setting impacts propagation speed and lookup frequency of MX records.
Technical article

Documentation from Microsoft Learn explains that the MX record with the lowest preference number (highest priority) is tried first. If it fails, the next MX record in priority sequence is used.

July 2023 - Microsoft Learn
Technical article

Documentation from Google explains that you can find MX records in your DNS settings provided by your domain host. Log in to your domain host's website, locate the DNS settings, and look for MX records.

July 2024 - Google
Technical article

Documentation from Cloudflare discusses the Time To Live (TTL) setting for MX records, recommending a low TTL for faster propagation of changes and a higher TTL for reduced DNS lookup frequency.

December 2024 - Cloudflare
Technical article

Documentation from DigitalOcean explains how to add and modify DNS records, including MX records, in their control panel. It details the required fields like hostname, record type, priority, and value.

March 2023 - DigitalOcean
Technical article

Documentation from RFC Editor defines MX records as DNS records that specify the mail server responsible for accepting email messages on behalf of a recipient's domain, and the preference value to use.

August 2023 - RFC-Editor