Si tu as vidé la Corbeille de ton compte email via clic D > "Vider cette corbeille maintenant" les messages qui s'y trouvaient sont perdus. En revanche si tu as supprimé certains (ou tous les) messages se trouvant dans la corbeille via clic D > "Supprimer ce message" elles restent récupérables tant que le dossier n'a pa été compacté.

This is a bit tedious, but it works. It does NOT work, though, if you have compacted trash since deleting.

1. click help>troubleshootinginformation
2. scroll to 'profile folders' and click 'open folder'
3. exit thunderbird
4. you are now in the profile. The trash folder will either be in the Imapmail folder, the Mail folder, or the Mail\Local Folders folder. Look for the trash, trash msf entries. IGNORE the msf file.
5. Open the file "Trash" with Notepad or a similar text editor.
6. Locate the line before your email text that reads "X-Mozilla-Status: 000X" (where 'X' is any character other than 0). Change the number to four zeros (″0000"). Repeat for all other messages. Save the document and exit Notepad
7. restart thunderbird and the messages should appear. Let me know how it goes. Please.

This is a bit tedious, but it works.

david, as I said in the first sentence of my answer: this doesn't work if the Trash folder has been emptied via R-click "Empty Trash" since Trash (or Deleted) folders are automatically compacted after the 'Empty Trash' command. Your method only works if Jean has not used the 'Empty Trash' command but only deleted messages from the Trash folder by selecting them and using the "Delete Selected Messages" command in the context menu