Does POP3 NTLM authentication mechanisms works correctly?

[SuhovDE]

Hello,

I tried to get email using Pop3Client, but received the following exception:

MailKit.Net.Pop3.Pop3CommandException POP3 server did not respond with a +OK response to the STAT command.

POP3 log contains the following lines:

Connected to pop://xxx.xxx.xxx.xxx:110/
S: +OK Microsoft Exchange Server 2003 POP3 server version 6.5.7638.1 (domain.net) ready.
C: CAPA
S: +OK Capability list follows
S: TOP
S: USER
S: PIPELINING
S: EXPIRE NEVER
S: UIDL
S: SASL NTLM
S: .
C: AUTH NTLM
S: +OK
C: CAPA
S: -ERR Logon failure: unknown user name or bad password.
C: STAT
S: -ERR Command is not valid in this state.
C: QUIT
S: +OK Microsoft Exchange Server 2003 POP3 server version 6.5.7638.1 signing off.

Is it correct that client send CAPA as answer for +OK? I thought, that it should send Base 64 encoded Type 1 message instead. See NTLM POP3 Authentication

FYI: After I cleared AuthenticationMechanisms property, the client was authenticated correctly, but using USER Mechanisms.

[jstedfast]

Okay, so the problem is that the POP3 server should not be sending +OK (which means "command finished successfully"), it should be sending just + (which means "go ahead and continue").

[jstedfast]

I've committed a patch that attempts to work around this broken server behavior. Can you give it a try and report back as to whether or not it fixes the issue?

[SuhovDE]

With this patch it works correctly.

Thank you for fix.

[jstedfast]

You're welcome!

[jstedfast]

I've released MailKit 1.6.0 with this fix