Possibilities: The global search is out of date, showing headers, but unable to connect to the actual email. How to fix a global search: https://support.mozilla.org/en-US/kb/rebuilding-global-database Maybe the folder containing the email is out of synch with the indexing file. Repair the indexing file. Locate the folder which should contain the missing email. right click on that folder and select 'Properties' click on 'Repair folder' button click on 'OK' re :''moving old mail to local storage'' By this, I presume you mean you are using 'Local Folders' mail account. A third possibility is that you only moved the headers into the 'Local Folders' account. So, search would locate the header, but the header cannot access the imap mail account nor server to download the email. One method: Suggest you use 'Copy to' rather than 'Move to' and check that the email can be opened and read once it is in 'Local Folders'. I synchronise folders for offline use to get an up to date copy in thunderbird, then in offline mode, copy emails to Local Folders. Check I can read them. Delete emails from imap account. Go back to online mode. Check your imap mail account 'Synchronise & Storage' settings in Account Settings. * https://support.mozilla.org/en-US/kb/imap-synchronization