If you get this error, you probably tried to run the older version of Mailbird. We do not support running the older versions, but you can try the following:
1. update Mailbird to the latest version using this installer:
https://download.getmailbird.com/installers/MailbirdOfflineInstaller.exe
2. Go to the Start menu in Windows, find Mailbird and then click "Check for updates".
