1 Topic by luxus (edited by luxus 2015-06-17 16:50:30)

  • luxus
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Topic: [SOLVED] SASL PLAIN authentication failed

I've recently upgraded my server (Centos) from 6.3 to 6.6 and upgraded IredMail (LDAP) from 0.8.6 to 0.9.1.
Now some of our multifunctionals and google get errors when sending e-mails.
Too many of those and fail2ban bans the ipadresses for an hour so they can't send e-mails.

The emails are sent to the recipient when the account is not banned.
I'm using Postfix 2.11.0 and dovecot 2.1.17

Here is a part of the messages in te maillog:

Jun 16 11:44:52 vcn-mail postfix/smtpd[22742]: warning: unknown[192.168.17.5]: SASL PLAIN authentication failed:
Jun 16 12:17:26 vcn-mail postfix/smtpd[29500]: warning: mail-qg0-f51.google.com[209.85.192.51]: SASL PLAIN authentication failed:
Jun 16 12:17:26 vcn-mail postfix/smtpd[29480]: warning: mail-qk0-f180.google.com[209.85.220.180]: SASL PLAIN authentication failed:
Jun 16 13:54:47 vcn-mail postfix/smtpd[20366]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 13:54:55 vcn-mail postfix/smtpd[20087]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 13:55:02 vcn-mail postfix/smtpd[20366]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 13:55:09 vcn-mail postfix/smtpd[16393]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 13:55:16 vcn-mail postfix/smtpd[17091]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 13:55:23 vcn-mail postfix/smtpd[20087]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 13:55:30 vcn-mail postfix/smtpd[20086]: warning: unknown[192.168.13.10]: SASL PLAIN authentication failed:
Jun 16 14:05:52 vcn-mail postfix/smtpd[20365]: warning: unknown[80.100.108.225]: SASL PLAIN authentication failed:
Jun 16 14:14:34 vcn-mail postfix/smtpd[20365]: warning: mail-qc0-f182.google.com[209.85.216.182]: SASL PLAIN authentication failed:

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2 Reply by SteveLuxe

  • SteveLuxe
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Re: [SOLVED] SASL PLAIN authentication failed

luxus: I was having this problem with one of my users on my mail server. It turned out that his email client was misconfigured. I had to whitelist his IP address with fail2ban, initially. Eventually, it got to the point where I was getting at least 15 or 16 failed SASL authentications a day for this user. The fix was to remove the mail server configuration from his machine, and re-add the account. After we added the account again, there were no more SASL Auth failures, and he could use his email again.

As a side-note, while this was happening, one of the symptoms was mail getting stuck in his outbox, and not being delivered properly. After we added the account again, everything worked fine. I'm not sure how many users you're dealing with, but if it's a small number, it's definitely worth purging their email configuration for your server, and re-configuring their account again. It's worth a shot, at least.

3 Reply by luxus

  • luxus
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Re: [SOLVED] SASL PLAIN authentication failed

I did some more digging and noticed that the base64 username / password combination was incorrect in the devices giving me problems.
I configured them to use LOGIN authentication and now it is working without any problems.

Thanks for your help.