Reject altered messages from your Subscribers (using DKIM).

DKIM (Domain Keys Identified Mail) is a technology for proving that emails have not been altered in transit.

As a security measure, reads DKIM headers before releasing messages to your Mailing List. If DKIM fails, the message sender is asked to approve.

This option is "on" by default.

How does it work? reads DKIM headers to check if the message changed "in transit".

If it did change, then the DKIM signature fails.

What happens next?

If the DKIM signature check failed, we ask your Subscriber to reply before releasing the message.

When will the message be released?

If your Subscriber replies and indicates the message is OK, we release the message to your List.

Will always ask that Sender for approval?

Once your Subscriber replies and confirms their messages are OK to send, we put their email address on the Exception List.

If that Subscriber's email fails DKIM in the future, we do not ask them to approve their messages again. We just release the message to your Mailing List.

Why does this happen?

DKIM is an email authentication method designed to detect forged sender addresses in emails. This is also called email spoofing, a technique often used in phishing and email spam.

Various things can happen at the sender's ISP that could also cause a DKIM failure.


Log into your mail-list account at

  • Click Customize Your List.
  • Click Miscellaneous Settings.
  • Click Reject Subscriber Messages That Fail DKIM Signing.
  • Click No to turn off this security option.
  • Click Save.

In this same Menu, you can also choose to enforce SPF settings (Sender Policy Framework). SPF verifies the email was sent from an approved IP address for the domain.

For more information about these email verification options, please see SPF, DKIM, and DMARC.