How to build an email allow list using MX records for initial email validation?
Summary
What email marketers say11Marketer opinions
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.
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.
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.
Marketer from Email Geeks suggests checking a domain against known Microsoft MX records to identify O365 domains and caching the results.
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.
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.
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.
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.
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.
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.
Email marketer from DNS Records notes MX records can point to subdomains as well as the primary domain, allowing for flexible email routing configurations.
What the experts say6Expert opinions
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.
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.
Expert from Email Geeks notes that MX records don’t change that often, so you can often cache for a while.
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.
Expert from Email Geeks says you can look up and cache MX records as they don’t change that often.
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.
What the documentation says5Technical articles
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.
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.
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.
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.
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.