Note: This article has the reference to the issue with the fix available:
- #PPPM-6939 "Under certain circumstances, Postfix failed to resolve short system email aliases,
such as “root” or “postmaster”, which resulted in emails being rejected with message
“Unable to get sender domain by sender mailname”."
- Plesk Onyx 17.5.3 Update 23 25 September 2017 (Linux)
DMARC is enabled at Plesk > Tools & Settings > Mail Settings
When the message is rejected, there are entries in /var/log/maillog:
CONFIG_TEXT: srv1 spf: SPF result: fail<...>
srv1 dmarc: DMARC: REJECT message for email@example.com<...>
srv1 postfix/smtp: 663B65D9FB: firstname.lastname@example.org, relay=mx.example.com[18.104.22.168]:25, delay=2.6, delays=0/0.02/2.1/0.4, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 20E631E1A31A7)
Trying to send an email using sendmail, the following error appears in
CONFIG_TEXT: Unable to get sender domain by sender mailname
This issue has been considered as Plesk bug #PPPM-6939
Update Plesk to the latest version as suggested in this article.