Question : Email 10060 error

I'm an independent contractor and I have several clients and I occasionally have to work out of their office.
  I have my primary email going to my AT&T Broadband cable account.  I have no problems receiving and sending my mail at home.
  But when I pickup my laptop and go to certain clients, my email will not receive nor send.  The error is:

  Protocol POP3,  Port: 110,  Secure SSL: No,  Socket Error: 10060,  Error number: 0x800CCC0E

  I can ping the AT&T email server ("mail.attbi.com") but it just won't work.

  I've tried the "Secure authentication" checkbox to no avail.

  AT&T Customer Service was no help other than "It should be working...".

  I'm suspecting a firewall issue at my clients.  

QUESTION:  Is this problem fixable and if so, what do I tell my client's network engineers to help alleviate this problem?

Answer : Email 10060 error

ATTBI will not allow access to their mail servers from hosts off their network.  They are using filters to prevent this and have no near term plans to change it.