The server is allowed to send messages from the local subnet without authorization on the server.
But the message is not delivered. The error in the logs is 421 mail error reading data. What could it be about? Below I attach detailed logs.
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: [192.192.2.1:25] connection accepted from [192.192.21.105:52504]
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Set smtp greeting to [mail.sp.by]
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 220 mail.sp.by
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: << EHLO Intellect5
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Set max data size to 51200 KB
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Set max received headers to 30
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Maximum recipient count set to 1000
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Wait for processing response at least 10 seconds
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: STARTTLS extension allowed
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: 8BIT MIME accepted
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: BINARY DATA extension allowed
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: PIPELINING extension allowed
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Set local delivery to all
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: DSN extension denied
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Set remote delivery to auth
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Greylist disabled
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: Set remote delivery to all
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-mail Axigen ESMTP hello
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-PIPELINING
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-AUTH PLAIN LOGIN
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-AUTH=PLAIN LOGIN
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-8BITMIME
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-BINARYMIME
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-CHUNKING
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-SIZE 52428800
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-STARTTLS
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250-HELP
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 250 OK
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: << STARTTLS
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 220 Ready to start TLS
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: << SSL: client hello, remote 192.192.21.105:52504, version TLS 1.3 (0304)
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: << SSL: client hello, remote 192.192.21.105:52504, 7 cipher suites: c00ac009c014c0130035002f000a
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> SSL: server hello, remote 192.192.21.105:52504, version TLS 1.0 (0301)
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> SSL: server hello, remote 192.192.21.105:52504, cipher suite c014
2021-01-05 10:09:46 +0300 16 mail SMTP-IN:00009CE1: >> 421 mail error reading data
2021-01-05 10:09:46 +0300 08 mail SMTP-IN:00009CE1: closing session from [192.192.21.105]
Hello Viktor,
Because the error is generated after the mail client is issuing STARTTLS command I could bet that the problem is related to the TLS negotiation between the mail client and the mail server.
Could you please send a screenshot from the SSL Settings configuration of SMTP Receiving listener configured for port 25?
HTH,
Ioan
Thank you. I already figured out the reason was in TLS.