Uninstalling Mailbird is done the usual way, from 'Programs and Features' if using Windows 7 for instance. Otherwise on Windows 8 you can search for "Programs and Features" and from there you can right click and uninstall Mailbird.
For Windows 10, search for Apps, at the Apps & Features, look for Mailbird, click it and then choose uninstall.
Uninstall from command line
Open command line by running "cmd.exe" command (*Windows Key* + R to open the 'Run' window, or find it in the start menu)
Type this in command line and press enter: msiexec.exe /x {4E757DEB-ED12-4A25-AA23-DEBF91B6C4CF}
For Older version of Mailbird (below 1.1.0.0)
Try running this command (*Windows Key* + R to open the 'Run' window, or find it in the start menu).
rundll32.exe dfshim.dll,ShArpMaintain Mailbird.application, Culture=neutral, PublicKeyToken=5ab9151dbc1ae0f0, processorArchitecture=x86