Email won't send out after installation of AVG

I have had AVG installed on my new computer downstairs for the last 5 months without issue.  I was very happy with it so when my wife's computer protection was about to expire, I loaded AVG onto that as well.  The next time she tried to use her email (Thunderbird), she could take messages in but could not send e-mail out.  The error message read as such: "An error occurred while sending mail: The mail server sent an incorrect greeting:  Service not available."  Oddly, my own system also now has the same error on outgoing messages.  While waiting for the installation on my wife's computer, I used the Zen platform to initiate a scan on my computer downstairs as well.  Both errors started the night I put AVG on the laptop.  I have tried swappign out the ports (25 to 587 and back) as well as changing up the security paths in the mail options of Thunderbird.  I have also turned off all e-mail scanning and allowed Thunderbird full access to the net but no change in the problem.  Any thoughts out there?

Hello James,
I apologize for the inconvenience caused. I do understand your concern. Could you please tell me which AVG product you have installed? Please feel free to contact us back.
Thank you.

Hello James,
I apologize for the inconvenience caused. I do understand your concern. Could you please tell me which AVG product you have installed? Please feel free to contact us back.
Thank you.