[SOLVED]undelivered mails don't return to right sender Hi all, Sorry if this problem was soon posted but I don't find any solution in forum. The only one could be http://www.howtoforge.com/forums/showthread.php?t=13762&highlight=returned+mail but it seems that the php code is right for me. So any undelivered mail send by php returns to "firstname.lastname@example.org" where myserver.net is the ISPConfig host. The mail is delivered to www-data so it fall in /var/mail/www-data, which grows... I have create a .forward file so I receive them now in my mailbox. The problem is that I don't understand why it don't return to the defined sender. The return mail is like this one (email@example.com is the sender on ISPConfig server, firstname.lastname@example.org is a non existent mail address) : But the original mail, joined to this one for information, says : The From and return-to fields are good.... Why Postfix send the error message to www-data ?