Custom MAPI dll is not working in some 32 bit windows OS

[RiyaShah]

Hello all,

I have created a simple MAPI dll with the help of following post:
http://www.cplusplus.com/forum/windows/103010/

The dll is created with target platform as 32 bits. Our requirement is to create a mail client which can be used as Default Email client using Right click menu -> Sento -> MailRecipient.

We have been testing this dll on many different environments, like 32 bit and 64 bit Windows and with all combinations of office versions (to send from office documents).

For the Right click menu -> Sendto -> MailRecipient (When set our application as default email client) is working well with all 64 bit OS (Windows 7, 8, 8.1 and 10) and also with 32 bit OS (Windows 10). But somehow, it is not working with Windows 7,8 and 8.1.

I checked all possible registry settings which are same for all. Plus, as mentioned earlier the dll is built to suit 32 bit environments, and it is working in Windows 10 (32 bit).

We have used all other default settings in project properties (except we have set Target Machine as Machine X86).

I have put logs in each MAPI function to check in which function it gets stuck. The problem is the dllMain is not called in 32 bit Windows 7, 8, and 8.1.

Could you help me to find out what the exact problem is?

Thanks,
Riya Shah.