Any ideas about this email problem?

[BeeDeeDubbleU]

Trying to answer an email enquiry and the reply is bouncing back with this message. I am using the email address provided by the enquirer. Anyone have any idea what is wrong?

"5.7.1 Inappropriate url reference, please remove link reference and resend message."

[Rob_Banks]

Do you have a link in the email body? More than one link?
I'd look at that.

[tangor]

If that URL embedded in the message body is found in the spam blocker lists many email servers employ (you can investigate that yourself) the message will be rejected. In fact, that reject/bounce should provide you with a link to same and you might visit and plead your case to that entity to allow your URL to pass.

5.7.1 errors generally indicate authentication of the message as an open relay (generally not allowed) over SMTP.