Problems with Group Contacts

I have created to Group contact list and when I compose an email add the Group Contact list to the To: box, write my email and hit send i get an error from McAfee. It states, Email Connection Lost. After you verify your computer is connected to the Internet, McAfee recommends that you resend those messages from your email program. I spent 3 hours on the phone with McAfee and they couldn't figure out the problem. I can send and receive email with no problems, just can't use group contacts. Can any one offer some advice. Thanks