I am running a multiserver ISPConfig setup. Server have been installed following howtoforge's howtos. They are both ubuntu 14.04.5 LTS. Master is named web and it works as expected after last update. There is a second server named mail and it has the following issue after updating from ISPConfig 3.1.2 to the latest 3.1.13. (I followed instructions, updated slave before master, reconfigured services on both). The issue was sneaky, as after the update everything went fine, until I updated a mailbox. After I update any mailbox (from different domains) the mailbox can't receive mail from outside anymore. I checked this even by creating a test mailbox, it's the same. In the postifx/dovecot log i have: Code: Sep 24 18:23:02 mail postfix/smtpd: NOQUEUE: reject: RCPT from host02.sender.dom[18.104.22.168]: 451 4.3.5 <[email protected]>: Recipient address rejected: Server configuration problem; from=<prvs=01234567890=s[email protected]> to=<[email protected]> proto=ESMTP helo=<host02.sender.dom> Also, the updated mailboxes in the mysql table dbispconfig.mail_user all have in common the sysuser field (1) I guess it means they were edited or created by admin and not by the client's account. That's true, BTW editing with the client's account changed anything. web also has mail role and its mail domains don't have the issue edited mailbox on the "mail" server only will receive mail from its own domain, and other domains on the server, after the mailbox update. I'm concerned I came into something I'm unable to further diagnose.