I deleted a large number of emails and the iMac trash icon is greyed out, preventing emptying the trash.
I deleted the iCloud trash items in Mail, but couldn't empty the "on this mac" trash because it didn't show any items.
iPod touch, iOS 5, iMac (Intel)
Right-click the Toolbar to Customize. Drag the greyed out icon to the trash, and insert a new one.
This worked for me.
If you delete email from within Mail it does not go into the iMac trash can. Therefore there is nothing to delete from the trash can.
The emails deleted while in Mail go to the Trash folder in Mail. You can see it in the list on the left below Inbox.
This sorted out my problem. My trash can icon in Apple mail was greyed out for my email accounts. I rebuilt it and it got sorted. Thanks!
trash icon is greyed out
