Reply #17: It sounds like someone used your email address to send spam

[Gman]

most outgoing email servers (there is an incoming server (usually POP3 or similar and an outgoing server, SMTP) now require your login as well as the same password you use for your outgoing email account. It could be that if you have an easy password for your email that someone figured it out and used your email and password to send spam. What you're getting is messages from the SMTP server advising of problems delivering the sent mail.

You may want to change your email password (which may require changing your password for your ISP) in order to prevent this from happening.

Spammers are constantly looking for SMTP servers to send their spam with so it's important that SMTP servers require a login and password to send email. THere is a list of domains out there that are "open" (i.e. no password required) and many incoming email servers will not accept email from them because they are capable of sending spam. So most responsible admins of email servers now require passwords for SMTP servers.

I maintain email servers for a couple of companies and every day I see "Relay Denied" in the log along with an email address that doesn't exist on our server because someone tried to use our server to send spam.