Hello everyone.
I got same issue. Port 25 opened. In /var/log/maillog got this entry which cannot understand:
Oct 31 17:25:22 mail postfix/qmgr[1946]: 4N1JyX1spjz4qxq: from=<sender@gmail.com>, size=3614, nrcpt=1 (queue active)
Oct 31 17:25:22 mail postfix/qmgr[1946]: 4N1KNJ0lc2z4qxy: from=<sender@gmail.com>, size=3617, nrcpt=1 (queue active)
Oct 31 17:25:22 mail postfix/pipe[101535]: 4N1JyX1spjz4qxq: to=<receiver@mydomain.co.uk>, relay=dovecot, delay=2174, delays=2174/0.03/0/0.06, dsn=4.3.0, status=deferred (temporary failure)
Oct 31 17:25:22 mail postfix/pipe[101536]: 4N1KNJ0lc2z4qxy: to=<postmaster@mydomain.co.uk>, relay=dovecot, delay=1042, delays=1042/0.01/0/0.06, dsn=4.3.0, status=deferred (temporary failure)
Oct 31 17:26:29 mail postfix/postscreen[101569]: CONNECT from [209.85.128.179]:36691 to [95.217.159.161]:25
Oct 31 17:26:35 mail postfix/postscreen[101569]: PASS NEW [209.85.128.179]:36691
Oct 31 17:26:35 mail postfix/smtpd[101573]: connect from mail-yw1-f179.google.com[209.85.128.179]
Oct 31 17:26:35 mail postfix/smtpd[101573]: Anonymous TLS connection established from mail-yw1-f179.google.com[209.85.128.179]: TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256
Oct 31 17:26:36 mail postfix/smtpd[101573]: 4N1Knm2dXcz4qyB: client=mail-yw1-f179.google.com[209.85.128.179]
Oct 31 17:26:36 mail postfix/cleanup[101578]: 4N1Knm2dXcz4qyB: message-id=<CA+Rmw=DWu86zfgU8wM2dQjOQM9xJ3u7c0VaEvQOF4cXOOy24Tg@mail.gmail.com>
Oct 31 17:26:36 mail postfix/qmgr[1946]: 4N1Knm2dXcz4qyB: from=<sender@gmail.com>, size=3728, nrcpt=1 (queue active)
Oct 31 17:26:36 mail postfix/10025/smtpd[101585]: connect from localhost[127.0.0.1]
Oct 31 17:26:36 mail postfix/10025/smtpd[101585]: 4N1Knm56wQz4qyF: client=localhost[127.0.0.1]
Oct 31 17:26:36 mail postfix/cleanup[101578]: 4N1Knm56wQz4qyF: message-id=<CA+Rmw=DWu86zfgU8wM2dQjOQM9xJ3u7c0VaEvQOF4cXOOy24Tg@mail.gmail.com>
Oct 31 17:26:36 mail postfix/qmgr[1946]: 4N1Knm56wQz4qyF: from=<sender@gmail.com>, size=4366, nrcpt=1 (queue active)
Oct 31 17:26:36 mail postfix/10025/smtpd[101585]: disconnect from localhost[127.0.0.1] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Oct 31 17:26:36 mail amavis[78949]: (78949-02) Passed CLEAN {RelayedInbound}, [209.85.128.179]:36691 [209.85.128.179] ESMTP/ESMTP <sender@gmail.com> -> <receiver@mydomain.co.uk>, (ESMTPS://[209.85.128.179]:36691), Queue-ID: 4N1Knm2dXcz4qyB, Message-ID: <CA+Rmw=DWu86zfgU8wM2dQjOQM9xJ3u7c0VaEvQOF4cXOOy24Tg@mail.gmail.com>, mail_id: 6dCRizRWd_VV, b: _Ez0CWvXQ, Hits: 0.286, size: 3728, queued_as: 4N1Knm56wQz4qyF, Subject: "Re: test", From: <sender@gmail.com> (dkim:AUTHOR), helo=mail-yw1-f179.google.com, Tests: [DATE_IN_PAST_24_48=0.485,DKIM_SIGNED=0.1,DKIM_VALID=-0.1,DKIM_VALID_AU=-0.1,DKIM_VALID_EF=-0.1,FREEMAIL_FROM=0.001,HTML_MESSAGE=0.001,RCVD_IN_MSPIKE_H2=-0.001,SPF_HELO_NONE=0.001,SPF_PASS=-0.001], autolearn=no autolearn_force=no, autolearnscore=0.287, dkim_i=@gmail.com, dkim_sd=20210112:gmail.com, 336 ms
Oct 31 17:26:36 mail postfix/amavis/smtp[101582]: 4N1Knm2dXcz4qyB: to=<receiver@mydomain.co.uk>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.52, delays=0.16/0.01/0.01/0.34, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as 4N1Knm56wQz4qyF)
Oct 31 17:26:36 mail postfix/qmgr[1946]: 4N1Knm2dXcz4qyB: removed
Oct 31 17:26:36 mail postfix/pipe[101535]: 4N1Knm56wQz4qyF: to=<receiver@mydomain.co.uk>, relay=dovecot, delay=0.05, delays=0.01/0.01/0/0.03, dsn=4.3.0, status=deferred (temporary failure)
Oct 31 17:27:06 mail postfix/smtpd[101573]: disconnect from mail-yw1-f179.google.com[209.85.128.179] ehlo=2 starttls=1 mail=1 rcpt=1 bdat=1 quit=1 commands=7
Oct 31 17:30:27 mail postfix/anvil[101484]: statistics: max connection rate 1/60s for (submission:unknown) at Oct 31 17:23:56
Oct 31 17:30:27 mail postfix/anvil[101484]: statistics: max connection count 1 for (submission:unknown) at Oct 31 17:23:56
Oct 31 17:30:27 mail postfix/anvil[101484]: statistics: max cache size 1 at Oct 31 17:23:56
Oct 31 17:35:22 mail postfix/qmgr[1946]: 4N1Knm56wQz4qyF: from=<sender@gmail.com>, size=4366, nrcpt=1 (queue active)
Oct 31 17:35:22 mail postfix/pipe[102051]: 4N1Knm56wQz4qyF: to=<receiver@mydomain.co.uk>, relay=dovecot, delay=526, delays=525/0.06/0/0.1, dsn=4.3.0, status=deferred (temporary failure)
can you please help me?
Kind regards