If you have a valid license key for the 2.x version that you do not want to upgrade, you may need the specific offline installer file (often named MailbirdSetup-2.9.x.exe ).
Since version 2.9 is an older build, ensure you are downloading the installer from the official Mailbird archives or a trusted software repository. Run the Installer: Open the downloaded .exe file. download mailbird 2.9