Hello all, This is my first active appearance in the forum, although I have been using it for some time now. I am the admin of an active server which is set up following this (perfect server) and was working fine for more than a year. Recently I decided to create SPF records and add DKIM signature functionality to outgoing emails, due to the fact that hotmail was putting to junks some messages from the newly created email mailboxes. So I followed this (for SPF) and this (for DKIM) and after some effort I managed to get it working and the messages were signed as they should be. During this process I noticed that in the original source of the emails there was: Received: from xxxxx.gr (localhost [127.0.0.1]) (xxxx.gr is another domain in the same webserver irrelevant to the sender) by xxxxx.server.com (Postfix) with ESMTP id 84E02300087 (xxxxx.server.com is the hostname of the server and it is not a valid domain name. I just name it like this) for <email@example.com>; Fri, 6 Mar 2015 23:16:30 +0100 (CET) So, while trying to fix this localhost thing I changed server ip through ISPConfig 3 interface, (System->Server Config->IP Address) from 127.0.0.1 to the real IPv4 address. In the same time, I enabled spamfilter (Normal) for a specific mailbox.(i dont think that this affected in some way, anyway I just mentions it) Well..... after these two actions, no more outgoing message is DKIM signed and there is a strange behaviour with SPF. permerror is often apppeared. I change these two actions to the initial condition but there is no process. Now things get worse. Gmail rejects my emails (almost 1 email is rejected out of every 2 I send), whether I send from an Android Mail App or SquirrelMail. Below you can see what I get as a response from Gmail. This is the mail system at host xxxx.server.com. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <firstname.lastname@example.org>: host gmail-smtp-in.l.google.com[2607:f8b0:400d:c06::1a] said: 550-5.7.1 [2a01:4f8:d16:1182::2 12] Our system has detected that this 550-5.7.1 message is likely unsolicited mail. To reduce the amount of spam sent 550-5.7.1 to Gmail, this message has been blocked. Please visit 550-5.7.1 http://support.google.com/mail/bin/answer.py?hl=en&answer=188131 for 550 5.7.1 more information. m1si28354qcf.22 - gsmtp (in reply to end of DATA command) I suppose that changing IP Address like this was not very clever (bravo Marios.....) . I checked many files that could be potentially affected by this, but didn't find anything... Any ideas???