A "relay" occurs when your from or reply-to address does not match the address of the SMTP server you are sending the mail through, like sending mail through "smtp.googlemail.com" but setting the "from" to be "[email protected]". Try selecting a from address that more closely matches what your outgoing mail server would expect, like "[email protected]". If that doesn't work, then reply with some more details as to what your outgoing server is, and what servers you are using to send the mail "from" (the part of the e-mail address after the @ sign).