Mattermost, Inc.

SMTP authentication fails

Hello,

I can’t get email notifications to work. Mattermost cannot authenticate against my SMTP server.

Connection unsuccessful: Failed to authenticate on SMTP server - 535 5.7.8 Error: authentication failed:

In /var/log/mail.log there’re these lines to be found at each attempt:

Jul 5 00:15:15 vmd9662 postfix/smtpd[2857]: connect from vmd9662.contabo.host[5.189.134.50]
Jul 5 00:15:15 vmd9662 postfix/smtpd[2857]: Anonymous TLS connection established from vmd9662.contabo.host[5.189.134.50]: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
Jul 5 00:15:17 vmd9662 postfix/smtpd[2857]: warning: vmd9662.contabo.host[5.189.134.50]: SASL PLAIN authentication failed:
Jul 5 00:15:17 vmd9662 postfix/smtpd[2857]: disconnect from vmd9662.contabo.host[5.189.134.50]

I configured my email client with the exact same settings and get this log output when sending an email:

Jul 5 00:03:14 vmd9662 postfix/smtpd[2623]: connect from ipservice-092-214-156-164.092.214.pools.vodafone-ip.de[92.214.156.164]
Jul 5 00:03:14 vmd9662 postfix/smtpd[2623]: Anonymous TLS connection established from ipservice-092-214-156-164.092.214.pools.vodafone-ip.de[92.214.156.164]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
Jul 5 00:03:15 vmd9662 postfix/smtpd[2623]: NOQUEUE: client=ipservice-092-214-156-164.092.214.pools.vodafone-ip.de[92.214.156.164], sasl_method=plain, sasl_username=mattermost@fluchtkapsel.de
Jul 5 00:03:15 vmd9662 postfix/smtpd[2659]: connect from localhost[127.0.0.1]
Jul 5 00:03:15 vmd9662 postfix/smtpd[2659]: 9834A244171D: client=localhost[127.0.0.1], orig_client=ipservice-092-214-156-164.092.214.pools.vodafone-ip.de[92.214.156.164]
Jul 5 00:03:15 vmd9662 postfix/cleanup[2660]: 9834A244171D: message-id=<…
Jul 5 00:03:15 vmd9662 postfix/smtpd[2659]: disconnect from localhost[127.0.0.1]
Jul 5 00:03:15 vmd9662 postfix/qmgr[12338]: 9834A244171D: from=…, size=1269, nrcpt=1 (queue active)
Jul 5 00:03:15 vmd9662 amavis[12364]: (12364-02) Passed CLEAN {RelayedOutbound}, SUBMISSION LOCAL [92.214.156.164]:40544 [92.214.156.164] … -> …, Message-ID: …, mail_id: qq7B1-HT9Tno, Hits: -0.998, size: 796, queued_as: 9834A244171D, 243 ms
Jul 5 00:03:15 vmd9662 postfix/smtpd[2623]: proxy-accept: END-OF-MESSAGE: 250 2.0.0 from MTA(smtp:[127.0.0.1]:10035): 250 2.0.0 Ok: queued as 9834A244171D; from=… to=… proto=ESMTP helo=<[192.168.1.72]>
Jul 5 00:03:15 vmd9662 postfix/smtpd[2623]: disconnect from ipservice-092-214-156-164.092.214.pools.vodafone-ip.de[92.214.156.164]
Jul 5 00:03:15 vmd9662 postfix/smtp[2661]: Untrusted TLS connection established to gmail-smtp-in.l.google.com[66.102.1.26]:25: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
Jul 5 00:03:16 vmd9662 postfix/smtp[2661]: 9834A244171D: to=…, relay=gmail-smtp-in.l.google.com[66.102.1.26]:25, delay=0.48, delays=0.03/0.04/0.17/0.23, dsn=2.0.0, status=sent (250 2.0.0 OK 1467669796 o10si86009wjs.136 - gsmtp)

Am I missing something obvious? Should I provide more information about my setup?

Masin
(removed all email addresses because forum software thought I wanted to post links)