On Monday 15 November 2004 20:22, Neil White wrote:
Hi all, I have got postfix running on SuSE 9.1 but have some problems. It runs as a backup MX for a sendmail server running on Redhat 9.
I am having a spam related problem, but I dont know where to begin... Whenever I enable postfix so that it is accepting external connections, spam levels rise. Where for example the backup MX runs on a host called mail.my.net I am getting spam in the form of subject@mail.my.net.
What amazes me is that NOWHERE (to my knowlege) is the hostname mail.my.net listed on the net - the solve purpose of this host is (at present) backup MX.
So my question is, how are spammers sending mail to domains for which this is backup MX and making the senders address appear to have come directly from the mail host ?
If the sender doesn't qualify his address, that is to say he doesn't include the @foo.com part, postfix will by default add on the local domain name to it (this, by the way, is why we sometimes see mail from someone@suse.com on this list when that person has nothing at all to do with suse, he/she just sent a mail with an unqualified sender and postfix at suse.com tacked on the @suse.com)