Without authentication I get
The message could not be sent because the server rejected the sender's e-mail address. The sender's e-mail address was 'firstname.lastname@example.org'. Subject 'testq', Account: 'pop.smithmontgomery.com', Server: 'smtp.sbcglobal.net', Protocol: SMTP, Server Response: '530 5.7.0 Authentication required', Port: 25, Secure(SSL): No, Server Error: 530, Error Number: 0x800CCC78
With authentication on this is what I get
Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Account: 'pop.domain.com', Server: 'smtp.sbcglobal.net', Protocol: SMTP, Port: 25, Secure(SSL): No, Server Error: 535, Socket Error: 10053, Error Number: 0x800CCC0F
On the computers that work, it's fine with or without authentication. It seems specific to the computers but I have no idea what the problem is, maybe some kind of spyware or something but nothing seems out of the ordinary, anyone have ideas on what to do? I suspect I'll have to torture myself with some hijackthis logs if it is spyware, but I'm hoping someone knows something simpler to solve the problem to try first.