Are you talking about a Pop or IMAP mail account?

What happens if you right click on 'test' folder and select 'compact'. Allow a little time for the process to complete and then check to see if the messages were actually deleted off the server.

It's a POP account.

The option "compact" doesn't solve the problem. The mails were already deleted from the folder "test" but not deleted from server.

Pop mail accounts usually download from server to computer Thunderbird Inbox for mail account and then delete the copy off the server, but these settings can be changed in Account Settings. In your case it would seem that the instruction is to leave a copy on the server. Access your Account settings for the Pop mail account and use these settings.

• 'Tools' > 'Account Settings' > 'Server Settings' for the mail account
• select: 'check for new messages at startup'
• select: 'Check for new messages every eg: 10 minutes'
• select: 'Automatically download new messages'

I would suggest that you leave emails on the server for a short period. Then, between your regular profile backups and the recent emails left on the server, you would be able to retrieve most if not all emails.

• select: 'Leave messages on server'
• select: 'For at most eg: 30 days'
• select: 'Until I delete them'

Selecting the above means that any emails not deleted and older than 30 days will be auto deleted. If you delete an email, it will be removed from server.

If you need to empty the Deleted folder each time you exit Thunderbird:

• select: 'Empty Deleted folder on exit'

• click on OK to save changes.
• Close and reopen Thunderbird.

Thank you for your answer, but I am afraid that I didn't make the problem completely clear.

I don't want all e-mails to be automatically deleted from server after 30 days. I want them to stay on server until I manually delete them through the web-based interface. (that is why I have chosen, both at "Tools > Account Settings > <account name> > Disk Space" and "Tools > Account Settings > Local Folders > Disk Space", the option "Don't delete any messages".)

The only e-mails that I want to be automatically deleted after 2 days are those in the subfolder 'test'.

How can I do that? Is it possible?

If you never want any emails to be deleted off the server by Thunderbird then use the options in (A) below:

• select: 'Leave messages on server'
• deselect: 'For at most eg: 30 days'
• deselect: 'Until I delete them'

- only select 'Leave messages on server'.

If you only want emails you delete to be removed off the server, then use options as described in (B) below:

• select: 'Leave messages on server'
• deselect: 'For at most eg: 30 days'
• select: 'Until I delete them'

do not select the 'For at most eg: 30 days' option.

The 'Retention Policy' tab for each folder means emails would be deleted off computer AND server option, it works as an additional option to Disc Space as set in account settings. So if you have set this up for the 'test' folder, then you would need to use the settings in Account Settings that are the same as (B) above. This would save you from manually deleting any deleted items off the server, but keep all other emails on the server. This is how to make this option automatic and work, but it will delete those items off the server.

It does not work if you have issued instructions to never delete off server under Account Settings > Disc Space and also selected to 'Leave messages on the server' but not selected any of the delete options.

To leave all emails on the server regardless of whether you have deleted them in Thunderbird, but delete emails from a specific folder in thunderbird only, you need to select the options as described in (A) above.

You could set up a Message Filter:

'Tools ' > 'Message Filters' and call it eg: 'empty test', to 'Manually run' and 'match all of the following' to filter any emails sent TO your email address (this should include all emails, but if you need to add another condition for another email address, then remember to set 'match any of the following') and perform the action to 'Delete Message', but as Message Filters only run automatically on the Inbox, you would need to do one of the following:

• select the 'test' folder
• 'Tools' > 'run filters on folder'

emails will be sent to Deleted folder.

or

• open Message Filters, select only that filter, then 'run selected filter on' and choose the folder, then click on 'Run now'.

Only the 'Deleted' and 'Junk' folders have the manual option to 'Empty Folder' by right clicking on folder and selecting that option. Otherwise, you would need to select the folder, highlight all emails using Ctrl+A and then use the delete button.

You can also set up Thunderbird to auto Empty the Deleted folder when you exit Thunderbird in Account Settings > Server Settings.

Remember to compact the 'test' folder on a regular basis. Either right click on folder and select 'compact' or you could compact all the folders in the account: 'File' > 'Compact Folders'.

You can also set up auto compact options in 'Tools' > 'Options' > 'Advanced' > 'Network & disc space' and select to 'compact all folders when it will save over eg: 10 MB in total.'