The bitness of mail clients must match with the bitness of CMOD Windows client.
For example, if a 32-bit mail application is used, a 32-bit CMOD Windows client will work, but 64-bit Windows client will not.
If a 64-bit mail application is used, only a 64-bit Windows client will work.
Recommend you install the latest level of the 64 bit client and test.
Ed Arnold