Letter Opener banner

When Letter Opener converts a winmail.dat attachment, a the Letter Opener banner appears on top of the email message.

If you don’t want to see the banner you can change your Letter Opener settings.

Settings

Simply go to Mail > Letter Opener for macOS Mail and untick “Show Letter Opener Banner”

Troubleshoot

If your banner shows something other than the conversion message click the following link:

Winmail.dat does not open