So someone accused you of sending them spam, and it's an email that you didn't even send? Here's how that can happen...
Spoofing is the term used for people pretending to be someone else when they send email. In other words, the "reply-to" email address isn't their email address, but rather some other poor unsuspecting person.
Email software allows you to enter a reply-to address that is different from your sending address. There are many legitimate reasons why you might want to do this. For example, if you have multiple email accounts, you might wish to send business mail from your personal account sometimes, but want any replies to return to your business account.
Spammers take advantage of this and use other people's addresses so that they won't recieve bounce-backs (emails that fail to reach the addressee) or the many complaints generated from spam.
Can you do anything about this, so that people know if the email is really from you? Yes! Click here for information on creating SPF records, which you may find helpful.
You can also tell people to use this method to check the email to see if it is spoofed before filing a complaint (click here).