As a result, archived messages may go missing, or previously deletedemailsmight suddenly reappear.

Here’s how to repairThunderbirdfolders in case this happens to you.

Instructions in this article apply to Thunderbird version 68.6.0 forWindows,macOS, andLinux.

Right-click the folder you want to repair and select Properties from the menu that appears.

This may not be necessary, but it can prevent potential conflicts.

Right-choose the folder you want to repair and selectPropertiesfrom the menu that appears.

Go to theGeneral Informationtab and selectRepair Folder.

Go to the General Information tab and select Repair Folder.

Open your MozillaThunderbird profile directoryon your setup and pick the desired account’s data folder.

IMAPaccounts are in theImapMailfolder;POPaccounts are found underMail/Local Folders.

Locate the.msf filesthat correspond to the folders you want to rebuild and move them to the trash.

Move the .msf files that correspond to the folders you want to rebuild to the trash.

Do not delete the corresponding files without the.msfextension.

Theemail clientwill rebuild the removed .msf index files, thus repairing your folders.