dovecot - Apr 2016 - WP8/Windows 10 mail app can't login, tries double auth

Attila Nagy writes:
> Are there anybody who could make WP8 (and W10 desktop clients it seems)
> devices working with Dovecot's POP3 server?
>
> The conversation looks like this:
> S +OK ready
> C CAPA
> S +OK
> S CAPA
> S TOP
> S UIDL
> S RESP-CODES
> S PIPELINING
> S AUTH-RESP-CODE
> S USER
> S SASL PLAIN
> S .
> C AUTH
> S +OK
> S PLAIN
> S .
> C AUTH PLAIN
> S +
> C <base64 auth string)
> S +OK[space]
> C USER username
> S -ERR unimplemented
>
> First I thought the extra space after that OK causes this, but removing
> it changed nothing.
>
> So these devices try to log in with AUTH PLAIN, then even after a
> successful login they want to log in again with USER, which gets rejected.
I dimly remember some Windows clients preferring either "LOGIN" or
"PLAIN"
style mechanism.  Have you tried allowing "LOGIN" style
authentication?

 	auth_mechanisms = plain login

Joseph Tam <jtam.home at gmail.com>

On 04/28/16 21:27, Joseph Tam wrote:
> Attila Nagy writes:
>
>> Are there anybody who could make WP8 (and W10 desktop clients it seems)
>> devices working with Dovecot's POP3 server?
>>
>> The conversation looks like this:
>> S +OK ready
>> C CAPA
>> S +OK
>> S CAPA
>> S TOP
>> S UIDL
>> S RESP-CODES
>> S PIPELINING
>> S AUTH-RESP-CODE
>> S USER
>> S SASL PLAIN
>> S .
>> C AUTH
>> S +OK
>> S PLAIN
>> S .
>> C AUTH PLAIN
>> S +
>> C <base64 auth string)
>> S +OK[space]
>> C USER username
>> S -ERR unimplemented
>>
>> First I thought the extra space after that OK causes this, but removing
>> it changed nothing.
>>
>> So these devices try to log in with AUTH PLAIN, then even after a
>> successful login they want to log in again with USER, which gets 
>> rejected.
>
> I dimly remember some Windows clients preferring either "LOGIN"
or
> "PLAIN"
> style mechanism.  Have you tried allowing "LOGIN" style
authentication?
>
>     auth_mechanisms = plain login
Yes, the effect was the same I remember.