iCloud email alias suddenly not working
I have an email alias that I’ve been using sporadically for years. At some point recently it stopped working. Mail sent to it bounces, and if I try to send an email, it says "Cannot send message. This message cannot be sent at this time. Try again later.” I have other aliases and they don’t have this problem. It’s enabled in the iCloud email preferences. I have tried disabling and then re-enabling it.
Any suggestions?
Mac mini