I am running my own Postfix instance. TLS certificates are from Letsencrypt, DANE and DNSSEC is working. Outlook. com is unable to send any mail to my Postfix instance, but closes the SMTP session with "QUIT" immediately after the TLS session has been established. I do not know why. The shortened log messages are
postfix/smtpd[3711792]: connect from mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827]
postfix/smtpd[3711792]: setting up TLS connection from mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827]
postfix/smtpd[3711792]: mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827]: TLS cipher list "aNULL:-aNULL:HIGH:MEDIUM:!SEED:!IDEA:!3DES:!RC2:!RC4:!RC5:!kDH:!kECDH:!aDSS:!MD5:+RC4:@STRENGTH"
postfix/smtpd[3711792]: mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827]: Decrypting session ticket, key expiration: 1719250679
postfix/smtpd[3711792]: mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827]: Reusing old session (RFC 5077 session ticket)
postfix/smtpd[3711792]: Anonymous TLS connection established from mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
postfix/smtpd[3711792]: disconnect from mail-mw2nam04olkn20827.outbound.protection.outlook.com[2a01:111:f403:2c0a::827] ehlo=1 starttls=1 quit=1 commands=3
I also have a complete dump of the traffic from the Postfix logs (log level 4 in Postfix) as well as a Wireshark trace.
But the essential message is that the Outlook SMTP server sends the SMTP command "QUIT" between the last and one-but-last message. However, I don't have a clue why it does so. I do not find any indication what might be wrong.
