Recommendations for deleting mail

IMAP users will likely find that when a message is deleted it remains in the mailbox with a line through it or a cross next to it until deleted messages are purged.

However it is possible to set Thunderbird so that deleted messages are automatically removed.

IMAP users

Tools > Account Settings > Server Settings (located under IMAP account name)

Next to the field 'When I delete a message:' click on the down arrow and select Move it to deleted folder

Also ensure to select Empty Deleted folder on Exit

POP users go to:

Tools > Account Settings > Server Settings (located under POP account name)

Select the option to Empty deleted folder on exit