~runxiyu/smlmp#1: 
Relay access denied

A plain unauthenticated SMTP connection to localhost:25 is an attempt to use the MTA as an open relay, which obviously won't work on properly configured MTAs.

Demonstration:

andrew@andrewyu:~$ nc localhost 25
220 mail.andrewyu.org ESMTP andrewyu.org (Debian/GNU)
HELO mail.andrewyu.org
250 mail.andrewyu.org
MAIL FROM: me@runxiyu.org
250 2.1.0 Ok
RCPT TO: andrew@noisytoot.org
554 5.7.1 <andrew@noisytoot.org>: Relay access denied
Status
REPORTED
Submitter
~runxiyu (unverified)
Assigned to
No-one
Submitted
1 year, 6 months ago
Updated
1 year, 6 months ago
Labels
No labels applied.

~runxiyu (unverified) 1 year, 6 months ago · edit

Make sure that smtpd_relay_restrictions in main.cf includes permit_mynetworks and things should work.

However, I wonder how GNU Mailman and other MLMs do it, since I don't recall needing to permit local relaying when using Mailman 2's SMTPDirect. Relying on relay access seems to be incorrect.

~runxiyu (unverified) 1 year, 6 months ago · edit

Please note that permit_mynetworks must come BEFORE any relevant reject... clauses such as reject_unauth_destination. Otherwise the email will be rejected.

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