unsupported auth mechanism

[Josef 'Jeff' Sipek]

On Mon, Aug 24, 2020 at 17:11:04 +0200, absolutely_free at libero.it wrote:
> Hi,
> 
> last friday I upgraded from dovecot-2.3.10.1_2 to dovecot-2.3.11.3 (FreeBSD).
> 
> Since then, I started having some issues with some customers.
> 
> The log I see is like:
> 
> pop3-login: Disconnected (tried to use unsupported auth mechanism): user=<username at domain.it>, method=USER, rip=x,y,x,z, lip=x,y,w,z, session=<e5KkR5qto8hPAL9q>
> 
> While, before upgrade, same user logged succesfully:
> 
> pop3-login: Login: user=<username at domain.it>, method=PLAIN, rip=x,y,x,z, lip=x,y,w,z, mpid=62876, session=<dMRmGWCtFtJtdcy6>

The only thing that comes to mind is the pop3 issue where an auth attempt
after a failed auth attempt would always fail.  I'm not sure why the client
that's having issues is failing the first attempt (unless it tries an
unsupported mechanism first, and then tries to fall back to PLAIN).  Anyway,
there is a fix on the master branch.

https://github.com/dovecot/core/commit/d0ea7f9f4530878a40ae0275cf0c36d3ff9111fc

You can try to patch the 2.3.11.3 code with it and see if that helps.
2.3.12 and 2.3.11.4 (if there is one) will have this fix.

Jeff.

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