Hello there Steven. We have read your message . We try to help you. Your crashing is causing problems of use with Thunderbird. We can try to erase the msf files in your profile. So that the indexes are going to be forced to recreate them. So we try to bypass the issue here. There is a simple way to remove them . This method work well for your pc. If it s worse then normal try this. Confirm that Mozilla Thunderbird is not open. Open its directory which is present on your computer. Select the account to rebuild its inbox.msf There will be two options – For IMAP accounts: ImapMail. For POP accounts: Mail/Local Folders. Select the corresponding .msf files which you wish to rebuild. Delete the .msf files or move the files which have .msf as an extension to the trash. Now start Mozilla Thunderbird, it will rebuild the deleted .msf index files. See the picture I have send along with this message. If you want to be shore Make a backup of your files. Greetings Firefox volunteer