Overview

The delivery of messages to list members that use GMail addresses may fail, with the following authentication-related messages in the logs:

<-- 550-5.7.26 This message does not have authentication information or fails to
<-- 550-5.7.26 pass authentication checks. To best protect our users from spam, the
<-- 550-5.7.26 message has been blocked. Please visit
<-- 550-5.7.26 https://support.google.com/mail/answer/81126#authentication for more
<-- 550 5.7.26 information. j82si4880265oih.160 - gsmtp

Information

Gmail requires that authentication information is configured according to their best practices, which are detailed in Google's article on how to Prevent mail to Gmail users from being blocked or sent to spam.

One of the proposed solutions is to configure DKIM and use strong keys and it is supported by Lyris LM.