Duplicating Spam Messages

[#1]

One of my family members had a historical problem with a large number of spam messages being sent to her personal Force9 e-mail account. She accesses her e-mail using Thunderbird IMAP. As Postmaster, I was asked to help. OK, I set up Thunderbird on another PC and quickly identified several source addresses that were responsible for a lot of messages and created some rules to identify them and move them to the Spam folder. There seemed to be some duplicate messages, so I installed a Remove Duplicates add-in to Thunderbird and ran that against the Spam. It identified thousands and I deleted them. Shortly afterwards, Thunderbird downloaded the same messages from the server. Back to square one, except there seemed to be more messages in the Spam folder than before. 

I tried using webmail, but that was having difficulty reading the large number of messages and would give up before I could do anything meaningful. I tried Select All in the Spam (aka Junk) folder but they couldn't be deleted. The server disconnects.

I have reported the problem to Customer Support, but apart from checking that spam filtering was enabled on the account, there wasn't much they could do. They opened a ticket and passed it on the BT.

Now, I can select all messages in Spam in Thunderbird and delete them. However, after a while the same messages come back. I have just done that again, 15,000-odd messages, and Compacted the folder, which Thunderbird says it has done.... Webmail says there are 15,000 messages in Junk, so that didn't work, and it disconnects if I try to delete even the maximum of 200 messages on one page.

Thanks for any suggestions as to what might be going wrong and how to deal with it, apart from deleting the mailbox, that is?

[#2 · Accepted solution]

With an IMAP client a 'delete' is actually a 'move' to the trash folder.  If that fails, (length of the query) the items will reappear when the folder sync refreshes.  Any of the following will mitigate what you are seeing...

• Increase the server time out setting - I suggest two minutes
• Delete fewer in one block
• Press and hold the SHIFT key when you click the DLETE button - in most clients that will actually delete the item, not move it to the deleted items folder - but be careful, there is no safety-net, undo or backout from this action

[#3]

Whoops, didn't mean to click This is an accepted fix. I was trying to turn it off... Thanks anyway!

I couldn't find a server timeout setting in Thunderbird, either globally or per-mailbox. I did try the Shift+Delete in Thunderbird. That is supposed to do an immediate delete, and the Spam folder did appear to be empty afterwards. It still does after closing and restarting. Webmail showed some 15,000 messages but ran out of steam trying to do anything with them.

It seemed to me that the messages were duplicating while I had Thunderbird running. I let it go until it seemed to have synchronised the Spam folder (which is not set to synchronise) before doing the select all + Shift+Delete. We'll see how that goes. Fingers crossed!