Subject does most of the work here, but I'll expand. [edit] Maybe if I had just RTFM'd harder I would've found my answers... I think this will help, but leaving the post up in case anybody else has ...
We are using Starlink in a remote place, which does not provide a SMTP relay server like our old (slow) cable modem ISP. A family member uses an email service she does not want to move away from that ...