Issue: The attempted install of Exchange 2013 CU5 was cancelled during the install process. Afterwards users could not connect to the secure imap service.
Cause: CU5 for exchange 2013 install was attempted on these servers, hence they were put in maintenance state by CU5. Also found out that only the person/software that put the server in maintenance mode can take it off maintenance.
Troubleshooting/Resolution: From powershell type, Get-servercomponentstate servername. Found out Imap proxy was in an inactive state.
Resolution: This registry fix(though not recommended by microsoft) resolved the issue. go to
HKEY_LOCAL_MACHINESOFTWAREMicrosoftExchangeServerv15ServerComponentStatesserverwideoffline
backup the servercomponentstates key
remove maintenance key
change functional key from 1:0:635407213073684026 to 1:1:635407212984929845 (Note that guid value is unique per server).
You are basically changing from 0 to 1 to make the server active. This activates all the inactive components
Ex-Shell 