Gmail Spam Warning emails to Commenters

We are testing this plugin to add to our blog and when the email is sent the commenter that there was a reply to the comment. It comes in on your computer @gmail.com as a spam warning. A bright orange banner saying:

Be careful with this message
Gmail could not verify that it actually came from XXX.com. Avoid clicking links, downloading attachments, or replying with personal information. There is a button to click to report the person as a spammer.

So how do you stop this? I don’t want to reported as a spammer.