Description

Starting from KES Windows version 12.6, it can parse third-party mail base files, but still can't re-assemble them. Malware scan tasks runs in folders where mail base files for Thunderbird or TheBat! are located and finds threats in old mail items.  

Diagnostics

After choosing Resolve or setting "Disinfect, delete if disinfection fails" in the KSC task, nothing changes, and another malware scan task anyway finds the same threats. 

Workaround and solution

Since KES cannot re-assemble third-party mail base files, it also cannot delete the mail items in them. 

It's required to perform manual deletion of infected mail items in mail base file, after that, compact folders in it.

1. Open mail base file in mail program (Thunderbird or TheBat!)
2. Find and delete the infected email (reported by KES)
3. Compact folders in the mail program

• guide for Thunderbird: https://support.mozilla.org/en-US/kb/compacting-folders
• guide for TheBat!: https://www.ritlabs.com/en/support/help/63/

Why it's necessary to perform compacting folders:

A deleted message is only logically marked for deletion, but physically, it still remains in the mail base file. Compacting folders will remove these items completely.