Hi bsstraw,
If turning off Norton Email Scanning does not have any effect on the issue, then it is almost certainly a problem with the ISP's servers. SMTP error codes are returned by the email servers and are displayed by Norton - Norton does not generate them.
I believe I found the root of the problems that i was having with Earthlink. When I referenced Earthlink's email setup info here: http://support.earthlink.net/articles/email/setting-up-outlook-2007-to-send-and-receive-email.php, I realized that my smtp server did not incluude "auth" and that my username did not include @earthlink.net as described therein. I believe making these changes has fixed the problem.
I was suprised to see the discrepencies since I have had my email set up this way since 2002.
Hi dkinhouston,
It is quite possible your ISP may have made a change on their servers. Sometimes things like "@earthlink.net" are techinically required but the ISP's servers allows it to work still. Perhaps a server upgrade or other change resulted in it being rejected without the fully qualified email address.
Earthlink has more than one email domain, it may have something to do with this.
Happy that you appear to have it worked out now.
Best wishes.
Allen