Relaying denied error message

Problem

• I tried to send mail to someone, but got an error saying:
  550 5.7.1 my_email@example.com;... Relaying denied. Proper authentication required.
• I can't send mail to anyone; I get this error for all mail I try to send.

Context

• I have set my SMTP server to outgoing.mit.edu.

Solution

• outgoing.mit.edu is strict about who it accepts mail from. It only accepts mail if your email has a From: address that is @mit.edu
• The solution is to change your email program so that your email messages say they are From your @mit.edu email address.

Note that if you prefer to read mail in a different account, you can have mail for your @mit.edu address forwarded to a different account. See Email Forwarding Options at MIT for how to set up forwarding that will cause mail sent to your @mit.edu address to be delivered to a different account.