said by BBStores:NETFIXER: Thanks for all your input. DNS seems to be working properly. I remoted into the laptop in question, added OpenDNS server names to the properties of the wired and wireless connections and the client Outlook errors did not change. Further research on this problem finds a solution posted 11/2012 that says: Log into this WEB based customer account at yahoo.com with the same Outlook email/pwsd parameters. Did that, and now the password request from the Outlook account goes away on SEND / RECEIVE, and I was able to send to the account, but the account labors to send out an email. Is this telling me ATT has an ACL problem? How could I find out what the ATT ACL setting are?
Ever since AT&T started using Yahoo! for their email service, there have been problems where individual email accounts had problems accessing and/or sending email in general or only from specific connections. Part of the problem is synchronization of the authentication between AT&T and Yahoo!, and can be DNS related wherein the client is connected to a different set of servers depending on which IP addresses are returned at any given time by a DNS query (which can change depending on the DNS servers being used, the physical location of the client, and the IP address being used by the client's PC.
What I have found to work for my notebook (since it is subject to using multiple DNS servers and getting different IP addresses depending on from where and how it connects) is to use only AT&T email servers (with Yahoo! being taken out of the equation). I have never had the random access problems if I use the POP3 and SMTP servers listed below (but as always, YMMV):
POP3: fpostoffice.isp.att.net, SSL, port 995
SMTP: fmailhost.isp.att.net, SSL, port 465
The nslookups for those servers partially shows why:
C:\>nslookup fmailhost.isp.att.net. 208.67.222.222
Server: resolver1.opendns.com
Address: 208.67.222.222
Non-authoritative answer:
Name: fmailhost.isp.att.net
Address: 204.127.217.18
C:\>nslookup fpostiffice.isp.att.net. 208.67.222.222
Server: resolver1.opendns.com
Address: 208.67.222.222
Non-authoritative answer:
Name: fpostiffice.isp.att.net
Address: 67.215.65.132
C:\>nslookup fmailhost.isp.att.net. 68.94.156.1
Server: dnsr1.sbcglobal.net
Address: 68.94.156.1
Non-authoritative answer:
Name: fmailhost.isp.att.net
Address: 204.127.217.18
C:\>nslookup fpostoffice.isp.att.net. 68.94.156.1
Server: dnsr1.sbcglobal.net
Address: 68.94.156.1
Non-authoritative answer:
Name: fpostoffice.isp.att.net
Address: 207.115.11.18
C:\>nslookup fmailhost.isp.att.net. 75.75.75.75
Server: cdns01.comcast.net
Address: 75.75.75.75
Non-authoritative answer:
Name: fmailhost.isp.att.net
Address: 204.127.217.18
C:\>nslookup fpostoffice.isp.att.net. 75.75.75.75
Server: cdns01.comcast.net
Address: 75.75.75.75
Non-authoritative answer:
Name: fpostoffice.isp.att.net
Address: 207.115.11.18
While OpenDNS does return a different IP address for the SMTP server than do AT&T and Comcast DNS servers, there is only a single IP address returned instead of round robin load balanced IP addresses as occurs with the outbound.att.net server. Some email clients have problems using SMTP servers that use round robin load balancing (especially if the client is configured to use SSL). Also, the two AT&T servers I have suggested are not CNAME values for Yahoo! email servers (as are the inbound.att.net and outbound.att.net servers), so the authentication synchronization between AT&T and Yahoo! is less likely to be a factor.
As for your question about how can you find out if you are on some AT&T or Yahoo! ACL banned IP address, there really is no way to find out because neither AT&T or Yahoo! is going to discuss their security with an outsider.
