SMTP Email Send Problem

I'm suddenly having sporadic problems accessing my ISP's SMTP server when sending mail. I can fail one minute and work 10 minutes or an hour later. It has been doing this now for a week. I have used Netscape email for years, currently on version 7.2 for some time now. My ISP is Comcast, so my outbound mail server is smtp.comcast.net, standard port 25 as always. I have made no changes to mail settings, login names, etc., no changes to my Norton settings (which yes include inbound and outbound mail scanning, but why should that suddenly start causing problems after being installed for months?) The only error message I get is from Netscape mail, which says a connection to the SMTP server failed (and of course then works 10-60 minutes later). Any ideas on why this would suddenly start being an intermittent problem? Thanks.

 

I believe that Comcast requires authentication of your username, when sending. However, it should not be erratic. May be you should stop scanning with the AV. That would, for sure, slow things down. I would try this first.
Have you tried Outlook Express?