Announcement List - welcome email

According to Dreamhost’s Wiki:

“Just set up to be a valid email alias (which can point to null if you don’t want to receive an email notifying you each time a new person subscribes), and then set up an auto-responder for that alias! Then make sure you DO have the emailit hidden input in your form on your web page.”

I set up the account, and set up the auto message, but when I manually join the list, I don’t get the welcome letter (only if I email the account directly). Help anyone?