Re: SMTP standards : needs outgoing SMTP server be MX for my domain?
> Actually, I see no good reason why outgoing mailer should be the same as MX.
There is none, other than maybe spam protection. There are setups which for instance check whether any mail with a sender @yahoo.com actually is coming from a yahoo.com mail server.
I see more good reasons for *not* having the primary MX function as an outgoing mailer, especially with large quantities of users.
> I am wondering if SMTP standards require that email sender of a domain be
> its MX? I find that really surprising.
Unauthoritative answer: no. Please double check.
P.S. You're not a known spammer, right? They could be faking it... ;-)