Are you located in the United States? If so then do not follow what designer said. The use of open relay's are a thing of the past, before you could just open up an port scanner and look for port 25's that were live, then put them in an smtp scanner and see which relayed mail. Now most are turned off to outside relaying and the ones that you do find are being abused so much that most major ISP's have them blacklisted. So even though our program says the mail is going out, it is actually not being delivered.

If you are outside of the United States and want to forge header information, then simply ask around for a proxy broker to buy proxies from to relay your mail. If you live in the United States and are serious about doing bulk mail then look into getting your own dedicated servers that allow bulk email (yes they do exist).

Start with at least 2, one server to host all of your valid from's and host whatever web sites and the second to actually send the email. You will want to purchase at least a half of a C block of IP's and attach each IP to it's own domain name to use as the valid from address. For these you can get the .biz or .info names for like $3 each. This way when an ISP does a reverse lookup on the domain name you are trying to send from, the IP address and domain name will match up and help get your mail delivered better. This does not guarantee that your mail will get delivered, setup spam assassin on your server or see if your current host has it setup and send yourself your own message you want to bulk out. Look at the headers and see what score you are given, anything under 5.0 will get delivered. Also keep in mind that if you are not rotating enough information in your message that score can sky rocket. The higher the number, the worse off you are. Heavy rotation in the email body is important, filling it full of random crap that most software generates will get picked up by most spam filters now a days.

There is a lot to bulk emailing, most of it you will not find in a guild of any kind. It comes from years of trial and error, because bulk email changes as time goes on. What worked two years ago is useless now.