Email issues since installing Norton

Hello, and apologies if this has been answered elsewhere. Im new and have had a quick look on the forum and googling but cant find the answer anywhere. The problem is this:

 

Since installing Norton Internet Security and Norton Power Eraser a couple of days ago, my Outlook is sending both gmail emails and btinternet emails as normal, showing them in the sent items folder, with no alerts or notifications to suggest they have not been sent.  My gmail emails are arriving with the recipients successfully but my btinternet emails are not. I have turned off my Norton outgoing email scanning and BT asked me to change my ports from 110 and 25 to their SSL ports which I have done just now but there is no change.

 

My pc was infected with 3 viruses picked up by Norton Internet security and one which was picked up by NPE and deleted.

 

I can send btinternet email successfully from my web browser and from my phone.

 

Is this a Norton problem, a virus that is not being picked up, a problem with the btinternet firewall/ account etc or something else???... Any help would be greatly appreciated. Thanks.