Yahoo mail failing only at client's site.

w_marquardt
w_marquardt used Ask the Experts™
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I have a client with an Internet issue when using Yahoo mail. This is a sbcglobal account. When they try to log on, the system will come back with a message that cprodmasx.att.com took too long to respond. This happens on all computers on their network in the office. It happens in all browsers. It happens with the AV installed or uninstalled. It does not happen when a computer is directly connect to the Comcast modem/router.

I'm not sure where to look for the answer to this problem. All of the other websites respond properly. I can get to gmail without a problem. There seems to be no other sites giving them issues. The mail does come through using Thunderbird as an email client. Unfortunately, they like the web interface and not the email clients like Thunderbird or Outlook. (Sigh...).

The email is accessible without a problem from anywhere offsite so it's not a site problem but something within the system. The only thing that I can think of is the hardware in the middle, the 24 port switch. It's an unmanaged switch so there's not a lot that can go wrong. Does this make sense to any of you? Is there something else that I might be missing (may with DNS or something else I'm not thinking of?)

If I do a traceroute, it get to a certain point out on the web (well outside of the local network) and then just keeps timing out. Traceroute to att.net resolves to the ip address properly.

I'd appreciate anyone's input on this one.
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Commented:
cprodmasx.att.com is related to AT&T u-verse. Are there any unauthorized devices connected to the switch? Maybe like a router?
Kevin StockmarSr. Network Engineer

Commented:
At this point, I would recommend taking packet captures on the host to determine where the latency/loss actually is;

1. Start a PCAP on the host
2. browse to Yahoo mail
3. Connect the laptop to the Comcast modem
4. Repeat the capture for the working
5. Compare the captures to determine where the latency is coming from

Once you have a better idea of source/dest/port/protocol/application, you can start checking the internal network to figure out where the packets are getting lost. I agree that it seems like there is a router sending traffic off in a different direction or a firewall in path blocking some traffic.

Commented:
1)   go to command prompt run as administrator and  run the command  " netsh winsock reset catalog "   (restart the machine and check)

2) do you have any additional domain controller in the network named cprodmasx.att.com ?


3) what is the Domain you have ?

if domain dns in user machines ... the forwarder configured properly ?

what the DNS and the Gateway ?

check these areas .. all the best
Commented:
I was able to convince the client to use Outlook instead of the web based email. That took care of all of the issues. Due to time constraints, I was not able to try the other possible solutions.

Thanks for all the help with this.

Bill

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