If you used 'Global Search' then you will not get a result if the email is in the 'Trash/Deleted' folder as that folder is not included in the search.

If you deleted an email then it usually goes to the 'Trash' folder of the account which might be called 'Trash' or 'Bin' or 'Deleted' etc. So you would need to select the 'Deleted/Trash' folder and either search using the 'Quick Filter' search for email address or manually through Thread Pane list.

Quick Filter bar can be enabled via: Menu app icon > Customise - select 'Quick Filter Bar'

If you use an imap account and the server has emptied the Trash, then when imap Trash synchronises with server it will get emptied, then the emails do not exist. For example: Gmail automatically empties the trash every 30 days. Other servers may delete more frequently eg: spectrum does it every 3 days and some servers leave it entirely up to you.

Thank you for the reply. I use Gmail. I need to investigate further exactly what's going on.

Some useful info: https://support.google.com/mail/answer/7401?co=GENIE.Platform%3DDesktop&hl=en#zippy=

Gmail also deletes emails older than 30 days from the Spam folder.

If you also access gmail via other methods eg: phone and if phone connects using pop then make sure the settings are set to 'Leave message on server' otherwise they get popped/deleted off the server. If accessing via imap and you delete a message, it gets put in gmail Trash. Then when you view using Thunderbird, that email will have been moved to Trash. Imap account folders synchronise to show what is on server, so emails/folders cannot be truelly deemed as independent copies in an imap account.

Sometimes, it might be necessary to rebuild an index if folders do not match what you can see when you access gmails webmail account. So if emails can be seen in webmail account, then try this in Thunderbird:

• Right click on folder and select 'Properties'
• click on 'Repair Folder'
• click on ok
• select another folder and then reselect the folder you 'fixed'.