Ringfinger, wellcome.
The best you can do now is:
a) if you use Outlook Express:
1. Close all your email programs
2. Run Mail Protection Wizard (see Start Menu > All Programs > avast! antivirus)
3. Remove all protection
4. Run Mail Protection Wizard again and choose 'All accounts' protection even in the future.
5. Configure avast to scan both Inbound and Outbound Mail
You can add a note into the email messages and see an icon on the system tray
6. Open OE and see what you get
7. If you not succeed, ctrl+alt+del and see if there is a file called ashMaiSv.exe running.
Let us know...
b) if you use MS Outlook
Just configure avast! pluggin to run (Outllook/Exchange provider)
Hope you'll be a happy avast! user like us!