We had fresh install of Exchange 2013 CU3 and found that the clients weren’t able to connect to exchange server over IMAP protocol. Telnet to the name and Ip of Exchange server on port TCP 143 (IMAP Port) was also failing.

Imap profile on outlook client was failing with following error

Log onto incoming mail server (IMAP): Your Server unexpectedly terminated the connection. Possible causes include server problems, network problems, or a long period of inactivity.

Strangely if we telnet localhost ( on port TCP 143, than we do get the IMAP Banner. Though

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An automobile enthusiast at heart and computer geek by profession, started my Career with MS in 2005.Left Jobs and started Pledge Technologies (the parent company to Grishbi) back in 2009.We have been providing IT consulting to various Small and Medium businesses across US and UK since then.Our company specialises in Microsoft Server technologies like AD, Exchange, the rest and with numerous Office 365 migrations under our belt, we quite an expert with that too. Whatever we learn in our day to day life, we share it back on Grishbi as a Thank for all the love and support our customers have given us.