We are in Exchange 2013 - 2010 Coexistence mode for the past two weeks, and are having some IMAP issues. One particular mailbox user is having intermittent issues with IMAP connection. About a dozen times a day, the connection fails, and the following is logged in the IMAP logs:
2014-08 05T20:19:03.041Z,0000000000036BDA,1,<2013CASIP>:993,<LOADBALANCERIP>:37619,<USERID>,61014,24,22,login,<USERID> *****,"R=""!@# NO LOGIN failed."";Msg=""User:<USER NAME>:ad73727b-7a7b-46d6-92d4-1c49d4ba3036:<DATABASE>:<2010MBXFQDN>;Proxy:<2010CASFQDN>:993:SSL;Proxy:<2010CASFQDN>:9933:SSL"";ErrMsg=ProxyTimeout:ProxyNotAuthenticated:PreAuthTimeout;Excpt=""No connection could be made because the target machine actively refused it <2010CASIP>:9933-SocketException"""
Notable section seems to be: Proxy:<2010CASFQDN>:993:SSL;Proxy:<2010CASFQDN>:9933:SSL"".
First, there are two "Proxy:" entries showing. During normal and successful proxy connections, there is only one:
014-08-05T19:46:01.846Z,0000000000036771,1,<2013CASIP>::993,<LOADBALANCERIP>:59894,<USERID>,241,24,25,login,<USERID> *****,"R=ok;Msg=""User:<USERNAME>:<GUID>:<2010DATABASE>:<2010MBXFQDN>;Proxy:<2010CASFQDN>:993:SSL;ProxySuccess"";ActivityContextData=14..."
Second, the 2010 CAS server is not listening on port 9933 but on port 993 (and 143). As a matter a fact, even on all 2013 servers, ProxyTargetPort value is not 9933, so not even sure where this number comes from. In IMAP logs it only appears in this specific log entry.
Other that this particular user, other IMAP services and connections seems to be working for most people on 2010 and 2013. I believe IMAP settings are thus set up correctly and I have gone thought them extensively.
I'm not understanding why the proxy is deciding, in some cases, to proxy to 2010 CAS server on port 9933 (at the same time as 993) for this particular user.
Any insight would be appreciated. Thanks.
ST