Reader Richard Applebaum wants deleted email messages really, truly deleted. He writes:
What I'm trying to achieve is a state where email in my Gmail account that I delete is entirely deleted. I find that when I delete messages they sometimes move to Trash, and sometimes go to Deleted Messages. I've also found that when I empty the Trash and Deleted Messages, the messages may still live on in Gmail's All Mail mailbox. How, in Apple's Mail, can I really get rid of these messages?
I'm pleased to report that MacRumors regular blairwillis his figured this one out. http://forums.macrumors.com/showthread.php?t=1229529. You'll want to take a gander at the process as originally outlined but here's the gist.
Via the Gmail website, click the Settings button (the one that bears a Gear icon) and choose Settings. In the resulting screen click Forwarding and POP/IMAP. Be sure that in the IMAP Access area Enable IMAP is enabled and that Auto-Expunge On -- Immediately Update the Server (default) is likewise enabled. If you've made any changes, click Save Changes at the bottom of the screen.
Now launch Mail, choose Mail > Preferences, select your Gmail account, and click the Mailbox Behaviors tab. In the Trash area be sure that both options--Move Deleted Messages to the Trash Mailbox and Store Deleted Messages on the Server--are enabled. From the pop-up menu below choose an interval after which the trashed messages will be deleted (your options are Never, One Day Old, One Week Old, One Month Old, and Quitting Mail). If you want to delete messages Right Now, you can do that manually, as I'll discuss shortly.
If Mail's sidebar isn't exposed choose View > Show Mailbox List. Find the entry for your Gmail account and if its contents aren't shown, click the Show item next to it to reveal its folders. Click the triangle next to the [Gmail] entry to show its contents. Select the Trash mailbox and choose Mailbox > Use This Mailbox For > Trash.
When you do so, this Trash entry will disappear from its present location. Instead, it will appear under Mail's main Trash heading. Now, when you delete a message, it will disappear from your Gmail Inbox (as well as from the All Mail mailbox) and move to this Trash mailbox.
If you'd like to delete those messages right this instant, Control-click (right-click) on this Gmail Trash mailbox and choose Erase Deleted Items. Confirm that you wish to do this in the sheet that appears and Mail will not only delete the messages from your Mac, but communicate with Gmail's server and instruct it to delete the messages there as well.