The people at Sage can’t do even the most simple of programming correctly.
As a result, using a 64-bit email program will fail. If you upgraded to the latest office and uninstalled your older version, you’ll find you can’t send emails anymore.
The solution is to install a 32-bit email program such as Outlook 2010 — this will mess up Outlook 2016 and you’ll need to repair the PST file. After you use ScanPST to repair the pst file, you’ll be able to use Simply again and use Outlook 2016.