Despite the threat to his immortal soul, a reader toys with one of the Big Commandments to learn why Mail.app can’t seem to delete his spam. Said Supplicant writes:
Help oh mighty Mac 911 gods.
SpamSieve to capture the massive amount of spam I receive with Leopard’s Mail application. It does a good job moving that junk to a Spam folder. However, when I delete those e-mails, they never delete. What’s weird is that I select all the e-mails in the Spam folder and delete them (either with delete key or contextual menu), they disappear from the Spam folder, but only temporarily. When I look in the Spam folder later, they’re still there. I now have over 10,000 messages in that folder and I can’t get rid of them.
This can happen when you have your IMAP account settings configured improperly. Try this:
Open Mail preferences and select an IMAP account. Click the Mailbox Behaviors tab and disable the Store Deleted Messages On The Server option. Close the Preferences window and click Save when prompted.
Still no go? Try disabling the Move Deleted Messages to the Trash Mailbox option for that account. Again, close the window and Save.
No? Really? Select the Spam mailbox and choose Mailbox -> Rebuild.