Hi everyone, I'm desperate: I have 3 IMAP accounts, all the same domain, same host (the German t-online.de). All of them have the same settings in mail.app The problem: - my mac is running ridiculously slow and heats up: activity monitor shows that mail.app takes up between 150 and 350% CPU (I don't know how that's possible, but whatever). - I noticed, one of the 3 accounts (let's call it account A) doesn't automatically receive emails. Not even when I hit "Get new messages". It only receives new messages when I quit mail.app an restart it. The other 2 accounts work normally. - When I go to mail->preferences ant disable account A, my problems seem to go away completely and mail.app is back to using about 15% CPU in Activity Monitor - additionally: for account A the Mailbox -> Rebuild function is greyed out. For the other two accounts it isn't I already deleted the envelope files in library->Mail->V3 I already deleted account A and set it up again. I already completely deleted a plugin called MailTags which I first thought was causing the trouble right after updating to El Capitan. It seemed to have worked for a day but then the trouble seemed to be even worse than before. I really hope you guys can help me out here!! Thanks!!