Microsoft Exchange Agents cannot be installed
Issue encountered
After installing GFI MailEssentials on Microsoft Exchange 2013 with Service Pack 1, the Exchange agents for GFI MailEssentials cannot be installed.
Cause
Microsoft released a patch for this issue, that was later incorporated into the cumulative updates. For further information see https://support.microsoft.com/en-us/help/2938053/third-party-transport-agents-cannot-be-loaded-correctly-in-exchange-server-2013
Solution
GFI MailEssentials fully supports Microsoft Exchange 2013 SP1. However, the latest cumulative update is required to avoid issues with the installation of Exchange agents.
For more information see https://technet.microsoft.com/en-us/library/jj983803(v=exchg.150).aspx