After recent change to AT&T Uverse Mail doesn't always work

Question

In the last two weeks I changed over from dsl to AT&T U-Verse. I set up the server info according to the instructions from AT&T, but now about every 10th or 15th time I try to "send" a new e-mail out OR reply to an e-mail I received I get this message: 'The SMTP server "smtp.att.yahoo.com" doesn't support authentification. Please check your account settings and try again.'
So, typically I then click 'try later', then go open the note I'm trying to send from the "Outgoing Mailbox" and click "send" and most of the time it goes on out as normal. Why does this happen...obviously it does support "authentification" since I turn right around and send it out using the same outgoing settings.
On a few occasions when this first happened, I went in and changed the outgoing server settings to turn off "authentification", but this didn't work either.
Any ideas?
Thanks!

Answer 1

I have U-verse (grumble, grumble,...caps..., grumble, grumble) and set up (10.6.5) Mail just to get it to work although I use Eudora as my preferred email client (lets not start a religious war here which would be off topic).  Prior to posting this I retested my Mail setup to verify it still works.  So here's how you set up both the ports...
In Accounts preferences, Account Information:
Description: anything
Email Address: whatever you want as a return address to appear in the "from" of your email
Full Name: anything
Incoming Mail Server: pop.att.yahoo.com
User Name: [email protected]
Password: should be obvious :-)
Outgoing Mail Server (SMTP): Select Edit SMTP Server List... to bring down a sheet to specify the smtp info.
In the SMTP Server List sheet use the "+" to create the server name smtp.att.yahoo.com for the account you are setting up.
In the Account Information tab:
    Set the Sever Name to smtp.att.yahoo.com
In the Advanced tab:
   Click the Use custom ports radio button and enter 465.
   Click checkbox to Use Secure Sockets Layer (SSL).
   Authentication: Password
   User Name: [email protected]
   Password: yet again :-)
Click OK to get back in the Accounts preferences click the Advanced tab.
In the Advanced tab:
   Set checkboxes per your desires.
   Port: 995
   Check Use SSL.
   Authentication: Password
That should do it.  I just listed all for completeness any others who might not know how to do it.  But I assume you have most of this already.  So basically specify the outgoing (smtp) port from the Accounts Information/Outgoing Mail Server/Edit SMTP Server List... sheet and the incoming port from the Advanced sheet.