That is very strange. I just did a test connection that I would expect to reproduce the error but it succeeded. I will need to investigate further. In the meantime, can you send it again?
For my own reference, the lists log line is 2021-02-01 12:00:44.958 [3135] H=eggs.gnu.org [2001:470:142:3::10]:59492 I=[2001:470:142::17]:25 X=TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256 CV=no F=<e...@gnu.org> rejected RCPT <emacs-de...@gnu.org>: relay not permitted Eli Zaretskii <e...@gnu.org> writes: > Please see the rejected message below. Why did lists.gnu.org say > "relay not permitted"? I sent this message via the SMTP server on > fencepost.gnu.org, so what relay is involved here? > > How can I avoid this failure in the future? TIA.