Exchange 2013 - IMAP GSSAPI authentication failure after installation of CU9

Hello,

Our environment consists of a mix of Linux/Windows and several of our Linux users have Thunderbird using Kerberos/GSSAPI to authenticate for IMAP/SMTP. This works perfectly for Exchange 2010.

We are in the migration process to Exchange 2013 and we noticed that GSSAPI/Kerberos was no longer available for IMAP. This has changed with the CU9 so we have installed this.

However after the installation the authentication to IMAP using Kerberos still fails even though it works perfectly for SMB/SMTP to the same server. A Kerberos ticket is created correctly for IMAP but the server rejects the authentication

2015-08-13T14:30:40.501Z,0000000000000015,4,10.0.0.200:143,10.0.0.10:36997,user,536,54,290,authenticate,GSSAPI,"R=""4 NO AUTHENTICATE failed."";Msg=""Auth:User:DOMAIN/user,Mbx:user@domain.com;System.Security.SecurityException:The user name or password is incorrect.\r\n"";LiveIdAR=OK;Excpt=""The user name or password is incorrect.\r\n-System.Security.SecurityException"";ExStk=

The EnableGSSAPIandNTLM is set to $true in the Set-imapsettings command.

Anyone know how to troubleshoot this issue?

Thanks,

Christophe

August 14th, 2015 2:56am

Set EnableGSSAPIandNTLM to $false and it should work
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August 14th, 2015 3:42pm

David,

Thanks for your answer.

We had done this but then the error message on the client changed stating that the server does not allow this authentication method, which seems very logical to me.

regards,

Christophe

August 17th, 2015 7:36am

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