Faking email sender

I have been receiving some spam addressed something like "asshole@server.com". But server.com admin checked and said that there are no email going out from that address.. Which by the way he says it does not exist. I noticed that the email is send from an ip from russia, while server.com is from usa.
Is possible that someone is faking server.com name? How is that possible?

It's called email spoofing, see below!

http://en.wikipedia.org/wiki/Email_spoofing

You can do it with telnet


#!/usr/bin/perl

use strict;
use warnings;  # Healthy coding

my $to = 'user1@domain.com, user2@domain.com, fag@dick.com';
my $from = 'nonexistant@email';
my $subject = "SPUFIN UP YO MAIL, BEE-YATCH!!!";

open(MAIL, "|/usr/sbin/sendmail -t");
print MAIL "To: $to\n";
print MAIL "From: $from\n";
print MAIL "Subject: $subject\n\n";
print MAIL "Body of the email, type whatever the fuck you want.";
close(MAIL);

print "...Complete!\n";

It might only work on internal mail servers... otherwise play around with sendmail, you'll get it eventually.