Why has sending mail from my home computer suddenly stopped working?

While there may be any number of reasons for the failure, lately there has been a trend among the big ISP's to start blocking outbound network traffic intended for mailservers on the internet, such as mail.cs.utexas.edu. The reason for the change is typically cited as spam prevention, a goal which the department supports fullheartedly. We recommend configuring your machine to connect with TLS or SSL encryption (see our faq entry: http://www.cs.utexas.edu/facilities/faq/406); if this fails please do not hesitate to email gripe [at] cs [dot] utexas [dot] edu and we will try to help you resolve the problem.