I've reviewed the instructions and they are the same as they have been in the past. Emailing has been working, but not anymore. The error is from the mail server, smtp error, not at the receiver. I've tried it with the default setting, with a Gmail account, and with a Yahoo account.
Also, since the error is "[SMTP_ERRORS--1]]" , and there is no error -1 listed (it starts with -2), it seems like something has gone wrong.
Maybe the last package update broke something.