Here I’m cheating a bit: all of my systems/containers without a dedicated local SMTP server use nullmailer to forward mails to my real SMTP server. So any tool trying to send mails sees a local mail server and can use that with no further configuration, I can them forward these mails using my regular MUA (that would be claws-mail for me).
CC: shironeko (npub1uzp…e7xt) Hailey (npub1qru…shcs)