How to 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 these 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?

Once you turn on this setting, will read DKIM headers to check if the message was changed "in transit".

If it was changed, then the DKIM signature failed.

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 will release the message to your list.

Why does this happen?

DKIM is an email authentication method designed to detect forged sender addresses in emails (email spoofing), a technique often used in phishing and email spam. (Wikipedia post)

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

Can prevent this from happening?

Once your Subscriber replies and confirms their messages are OK to send, we will put their email address on the Exception List. If that Subscriber's email fails DKIM in the future, we will not ask them to approve their messages again. We will simply release the message to your mailing list.


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.