Requests for contact info.

I've had several emails from potential buyers. And I've
replied with my contact info with no phone calls.
I had my wife get on the site and send me an email asking
for contact info, and when I replied CarGurus sent her an
email that I may be trying to bypass a security something
or other and to be suspicious of me as a seller.  
I don't know why this would happen and I'm sure I've lost
a sell or two because of this.  What going on with this and
how do we fix it. Getting fed up.