I hope this does not happen to you, but sometime when we uninstalled or delete something in Mailbird it might leave residue of files and registry that can caused problem when you do want to install Mailbird again. On this KB article I will tell you how you can do a clean uninstall with Mailbird that leave nothing behind. So if you can't uninstall Mailbird or want to make sure that you do a clean uninstall, please follow this steps
1. Download Revo uninstaller from this link
2. Double clicking the Revo exe file that you just download and followed the on screen instruction to install Revo Uninstaller
3. Run Revo Uninstaller
4. You'll see something like the above picture. Click on the marked search box and type Mailbird
5. Select Mailbird and press uninstall on the top tab
6. You'll see an uninstall dialog box from Windows, follow the instructions and uninstall Mailbird
7. After uninstall is finished press the advanced scan button then press the scan button like the picture above
8. Wait until scanning is complete then press select all, delete the leftover then click the next button.
9. Once again press select all and then press finish
10. That's it all Mailbird files and registry entry is now removed from your PC
If you are still having issue with Mailbird after this, please contact firstname.lastname@example.org.