The department’s SMTP relay, gateway.EECS.Berkeley.Edu, accepts incoming connections on the SMTP Submission port
Most of the major Internet Service Providers (ISPs) are now blocking or
filtering the default SMTP port (25) at their network borders, making
the use of gateway.eecs impossible for some home users. Those who are
being affected by their ISP’s blocks may find relief by using this
alternate port 587.
See the IRIS Software FAQ for instructions on how to configure your email client.
[2005-03-23 11:17:29 | Yi Ding, EECS Helpdesk]
SBC has a webpage about it’s port 25 blocking including a link to opt out at http://help.sbcglobal.net/article.php?item=4640 .