Roundcube autoresponder emails not delivered to Gmail accounts

Symptoms

• An autoresponder is configured in Roundcube via Settings > Filters.
• Roundcube automatic replies are sent with empty sender.
• The auto reply is not received by Gmail accounts.
• The following entry is found in /var/log/maillog:

Your email has been blocked because the sender is unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM. 550-5.7.26 550-5.7.26 Authentication results: 550-5.7.26 DKIM = did not pass 550-5.7.26 SPF [] with ip: [203.0.113.2 ] = did not pass 550-5.7.26 550-5.7.26 For instructions on setting up authentication, go to 550 5.7.26 https://support.google.com/mail/answer/81126#authentication a640c23a62f3a-a8988f40789si300814366b.20 - gsmtp (in reply to end of DATA command))

• The SPF, DKIM and DMARC records are correct.
• The Roundcube autoreply is received by users on other mail providers.
• The message is received on Gmail when the Auto-Reply option in Plesk is used instead.

Cause

The auto reply messages via Roundcube use the Sieve extension "Vacation" which sends auto-replies via sendmail from popuser with <> as sender to prevent loops.

Jan 1 00:00:00 server postfix/qmgr[1111111]: 1A234B5C6: from=<>, size=111, nrcpt=1 (queue active)

Therefore, the sender cannot be authenticated and Gmail rejects message because their system requires all messages to be authenticated.

Resolution

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