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windowsoutlookmapimapisendmail

32-bit MAPI app with 64-bit Outlook

The 32-bit version of our app is unable to send email using MAPISendMail with 64-bit Outlook installed. It returns an error 0x80004005, about which I can find little information beyond the fact that it seems to be a MAPI initialization error.

According to this MSDN document, MAPISendMail is the one exception to the rule that 32-bit apps can't use 64-bit MAPI. And yet it doesn't work (at least with XP and Vista--we haven't tested Win7/8 yet).

Can anyone shed any light on this?

TIA

Solution

  • There are no exceptions: a 32 bit process cannot load a 64 bit dll. When you have the 64 bit version of Outlook, the 64 bit version of mapi32.dll contains the actual implementation. The 32 bit version of mapi32.dll is a stub that does nothing but return an error.