localhost / postfix

[tvalleau]

I'm noting here that "localhost" or "127.0.0.1" (the same thing) do not work for SMTP server. (I have Postfix enabled, and use if for the SMTP server for other automatic emails, as well as Apple's Mail program.)

[Paul Collins]

It looks like IP addresses do not work in the Outgoing Mail Server field. We'll work on this. Meanwhile, if you happen to have a full host-domain name that points to your Mac, you should be able to use that. Perhaps one was automatically assigned by your ISP.

Another option: Use smtp.gmail.com and configure your Gmail account to permit use of your own email address instead of your Gmail address.