Can't resync mail in Migrator: Failed to copy mail content of subscription. Most probably that happens because of a network-related issue

Symptoms

• Plesk Migrator fails to resync mail messages

• The subscription details in Migrator show this error

  Failed to copy mail content of subscription. Most probably that happens because of a network-related issue. Check network connections between source and target servers, then run migration for that subscription once more.

• The following is logged to C:\plesk_migrator\rpc-agent\debug.log on the source server.

  IOError: [Errno 13] Permission denied: 'C:\\plesk_migrator\\MailMigrator.exe'

• The process MailMigrator.exe is present on the source server's Task Manager

Cause

MailMigrator.exe is stuck.

Resolution

1. Connect to the source server via RDP
2. Open Task Manager
3. Terminate MailMigrator.exe
4. Resync mail messages