I'm not a Mac user and don't have any significant experience with Parallels. But since nobody else has answered your real question, here are the only two suggestions I can think of.

You could try removing and reinstalling the Sage 50 E-Mail Writer. Here are instructions copied from the knowledgebase.

Section I: How to remove instances of the e-mail writer

1. Select Start, then Devices and Printers.
2. The Sage 50 E-mail Writer may appear under several different names.
3. Pick one of the instances if you have more than one, right-click on it, then select Remove device.
4. Select a printer, then select Print Server Properties.
5. Select Drivers tab.
6. Remove the Amyuni Document Converter, and then select Remove Driver and Driver Package.
7. Repeat the above steps until all of the instances of the E-mail Writer have been removed.

Section II: Reinstalling the Sage 50 E-mail Writer

• Run repair on the Sage 50 program using the installation files
• See Article ID 10602: How to run Repair.

The only other suggestion I have is that you consider using a hosting service instead of using Parallels. It will mean ongoing hosting fees but you won't have configuration problems.