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Email Protocols

MX Record(Mail Exchange Record)

A DNS record that specifies which mail servers accept email for your domain.

Definition

An MX (Mail Exchange) record is a type of DNS record that directs email to the correct mail servers for a domain. When someone sends an email to [email protected], their mail server looks up your domain's MX records to find where to deliver the message. MX records include a priority number, allowing you to set backup servers if the primary is unavailable. Without MX records, a domain cannot receive email at all.

Why It Matters

Properly configured MX records are essential for receiving email. For email marketers, MX records are important when validating subscriber email addresses. Checking if a domain has valid MX records is a key step in email verification to ensure you are sending to deliverable addresses. If you sign up a subscriber with an email at a domain that has no MX records, your email will always bounce.

How It Works

MX records are configured in your domain's DNS settings. Each record contains a priority value (lower number means higher priority) and a mail server hostname. When sending email, the sender's server queries DNS for MX records, tries the lowest priority server first, and falls back to higher priority servers if needed. This priority system ensures email delivery even if your primary mail server is temporarily unavailable.

Example

Here is an example of MX records for a domain using Google Workspace:

example.com    MX    1    aspmx.l.google.com
example.com    MX    5    alt1.aspmx.l.google.com
example.com    MX    10   alt2.aspmx.l.google.com

The numbers (1, 5, 10) are priorities - lower numbers are tried first. When someone emails [email protected]:

  1. 1The sending server first tries aspmx.l.google.com (priority 1)
  2. 2If that fails, it tries alt1.aspmx.l.google.com (priority 5)
  3. 3Finally, it tries alt2.aspmx.l.google.com (priority 10)

This ensures email is delivered even during partial outages.

Best Practices

  • 1Always set up at least two MX records with different priorities for redundancy
  • 2Use reliable, professional mail servers as your MX hosts
  • 3Keep MX record TTL (time to live) around 3600 seconds for reasonable propagation
  • 4Verify MX records after any DNS changes to ensure email delivery continues
  • 5Check MX records for domains you are sending to as part of list verification

Email Verification

Sequenzy checks MX records as part of email validation to ensure your subscriber addresses are deliverable.

Learn More

Frequently Asked Questions

You can check MX records using online tools like MXToolbox, or use command line tools like 'nslookup -type=mx yourdomain.com' or 'dig mx yourdomain.com'. Your domain registrar's DNS management panel also shows your MX records.

Yes, and you should. Multiple MX records with different priorities provide failover. If your primary mail server is down, email is routed to the next server in priority order. Most email providers give you 2-5 MX records to configure.

MX record changes typically propagate within 24-48 hours, though it can be faster. The propagation time depends on the TTL (time to live) value of your old records. During propagation, some emails may go to the old server and some to the new.