There is the mail_max_userip_connections setting, which helps for dealing with number of connections at any given time, but I'm looking for something that will help deal with users who configure their mail clients to connect too frequently.

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It would be really great if there were a way to tarpit those users to slow them down, or send them an imap message saying they are connecting to often and connections have been disabled for the next 5 minutes or something.

There might be an unintended consequence: I see connection spikes when users try to do a global string search across mailboxes.

Joseph Tam jtam.home@gmail.com