What is MAPI(Messaging Application Programming Interface)

Messaging Application Programming Interface (MAPI) is a messaging architecture and a Component Object Model based API for Microsoft Windows. MAPI allows client programs to become (e-mail) messaging-enabled, -aware, or -based by calling MAPI subsystem routines that interface with certain messaging servers. While MAPI is designed to be independent of the protocol, it is usually used with MAPI/RPC, the proprietary protocol that Microsoft Outlook uses to communicate with Microsoft Exchange.

More on Wikipedia :http://en.wikipedia.org/wiki/Messaging_Application_Programming_Interface

Hanging application OUTLOOK.EXE

Solution 1:
1. Register an important send/receive library file.  Go to Start > Run and type regsvr32 inetcomm.dll
2. Check if antivirus email check is slowing sending and receiving.  Disable it.
3. In the account settings, Advanced settings, change the server timeout time from 1 min to 5 min
4. Check if outgoing mail server authentication is required. Select that option in account settings and use same settings as incoming server
5. Your ISP may be blocking port 25. Try using alternate port 587.
6.  Check with email provider Tech Support to determine if server is having trouble.

Solution 2:
Repair Outlook by following instructions at:
http://office.microsoft.com/en-us/outlook-help/repair-an-ost-or-pst-file-in-outlook-HA001056300.aspx

For more details check this out:
http://forums.techguy.org/business-applications/742774-solved-outlook-exe-error.html

http://www.slipstick.com/problems/nosend.htm