I'm inclined to think, after reading alot of posts from many different users, who are all experiencing the same thing you describe, and many of them say they are using AT&T (Bellsouth), that this is an issue with the ISP.
Don't make any changes to your computer. Give your ISP a call.
If you have AT&T (Bellsouth), the phone # to DSL Support is 1-888-321-2375.
I have AT&T (Bellsouth). Yesterday I tried to reply (by email, Outlook Express) to a text messg my nephew sent to my phone (I have text messaging blocked on my phone, so it gives me the web pg addr/password to go view the text message), and I hit Reply, which brought up an Outlook Express blank email addressed to my nephew's phone #.
I typed a reply, hit send, and it wouldn't go through. I tried twice. I got the "not our customer" message.
I didn't recognize it for what it was..........I thought perhaps my nephew had a cell phone with a different company or something.
I haven't been in my email today, and I tried just now.
I received a BOATLOAD (aaaargh) of new emails.
I sent a test email to my son (yahoo email address) (twice), and another one to myself (bellsouth email) and got the following error message:The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'firstname.lastname@example.org'. Subject 'test 2', Account: 'mail.bellsouth.net', Server: 'mail.bellsouth.net', Protocol: SMTP, Server Response: '551 not our customer', Port: 25, Secure(SSL): No, Server Error: 551, Error Number: 0x800CCC79
I did confirm that you CAN
go to the web page and read AND SEND
email: (I keep a shortcut to it in my Bookmarks Toolbar (Firefox), just in case Outlook Express or the AT&T server experiences "technical difficulties"):https://login.yahoo.com/config/login?.src=m...mp;.partner=sbc
What's strange is that I kept trying (hitting Send/Receive) in Outlook Express, and then some went through (sent).
The first one I sent to my son's yahoo email went through and the one I sent to myself (bellsouth email) went through, but the 2nd test to my son's yahoo email DIDN'T go through.
So the problem is definitely in the AT&T (Bellsouth) server, and it is SPORADIC.
Hope that helps lessen your frustration somewhat, knowing that you aren't the Lone Stranger on this issue