It is possible to create an email server program that can send email as though it is from you.
I have done this for a court that wanted to send automated emails regarding filings. The return email address was set by the program. Many spammers use this method to send thousands of emails at a time. They obtain the email addresses from emails that are not cleaned up before sending.
The following is from an article that I found on cleaning up your emails. I do not know who the original author is.
Every time you forward an email there is information left over from the people who got the message before you, namely their email addresses and names. As the messages get forwarded along, the list of addresses builds, and builds, and builds, and all it takes is for some poor sap to get a virus, and his or her computer can send that virus to every email address that has come across his computer. Or, someone can take all of those addresses and sell them or send junk mail to them in the hopes that you will go to the site and he will make five cents for each hit. That's right, all of that inconvenience over a nickle. How do you stop it? Well, there are several easy steps. Try the following if you haven't done it before:
(1) When you forward an email, DELETE all of the other addresses that appear in the body of the message (at the top). That's right, DELETE them. Highlight them and delete them, backspace them, cut them, whatever it is you know how to do. It only takes a second. You MUST click the "Forward" button first and then you will have full editing capabilities against the body and headers of the message. If you don't click on "Forward" first, you won't be able to edit the message at all.
(2) Whenever you send an email to more than one person, do NOT use the To: or Cc: fields for adding email addresses. Always use the BCC: (blind carbon copy) field for listing the email addresses. This is the way the people you send to will only see their own email address. If you don't see your BCC option, click on where it says To: and your address list will appear. Highlight the address and choose BCC: and that's it, it's that easy. When you send to BCC: your message will automatically say "Undisclosed Recipients in the "TO:" field of the people who receive it.
(3) Remove any "FW:" in the subject line. You can re-name the subject if you wish or even fix spelling. And clean up the checked by AVG Avast etc on the bottom as well
(4) ALWAYS hit your Forward button from the actual email you are reading. Ever get those emails that you have to open 10 pages to read the one page with the information on it? By forwarding from the actual page you wish someone to view, you stop them from having to open many e-mails just to see what you sent.
