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What ports does Exchange MAPI/CDO use to connect to the Client Access Server from the Mailbox Server. I have a piece of software installed on a Mailbox server that uses Exchange MAPI (RDO to be specific, which uses Exchange MAPI). The problem is I'm running into MAPI_E_NETWORK_ERROR problems so I was wondering if there might be firewall issues i.e. the Client Access Server (CAS) cannot be accessed properly from the Mailbox server by MAPI. what ports do I need to check in the firewall configuration? This is on Exchange 2010

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up vote 3 down vote accepted

MAPI actually uses RPC which uses a dynamically assigned port number. Here's a blog posting that will help you make that port number static:

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Thanks, does it use only RPC? – Hannes de Jager Mar 1 '11 at 8:41

Check whether your Client Access servers are requiring encryption (use Get-RPCClientAccess to see). I've encountered problems with third party apps that don't support RPC encryption when the CAS are enforcing it.

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Thanks, already checked that. As far as I know this encryption settings is now actually on by default in 2010 whereas is was off by default in previous versions. – Hannes de Jager Mar 2 '11 at 7:17

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