• Update thunderbird
• Disable all add- ons
• Disable all the antivirus
• Use compatibility mode
• Use clean installation and remove all corrupted files
• Always use safe mode
• Clear all cache and all bookmarks

Mozilla Thunderbird is an open and cross platform for emails, news, RSS etc. It is a light software with RAM and data consumption. It is known as popular and smooth optimization browser. It  is top rated global email application to send or receive mails in secure method with very unique features.

Close all Thunderbird process

• Click on the start and type Run and press
• Type tskmgr to open task manager in the  Run window
• Click right on taskbar
• Select task manager
• Now go to processes
• Close Mozilla Thunderbird

For Windows

• Click on the start and open the Run
• Go to run window and type “%appdata%”
• And press the enter
• Now open the thunderbird folder and select the profiles
• Open the folder
• Delete the lock file

For Mac

• Open the finder
• Use “command+shift+g”
• Type (Library/Thunderbird/Profiles) and press return
• Open the home folder
• Go to the library folder
• Now open the thunderbird
• Search and open the profile
• Open your profile directory
• Open the terminal window and type “cd”
• Go to finder and immediately follow “cd”command
• Press return to run the command and type ‘rm -f .parentlock.’ command