> > On Sep 26, 2017, at 11:23 PM, Michael Fox <n...@mefox.org> wrote: > > > > BTW, the mail provider found that the default sendmail config and their > own > > customized config both rewrote the From: header when the From: address > was > > for a domain that had a CNAME record. They said this is a config option > in > > sendmail and they prefer to operate this way. Interesting that my other > > Postfix machines don't do this, nor do many other large email providers. > > This is an obsolete option in Sendmail that violates decades old SMTP > standards, CNAME canonicalization of recipient domains went away in > RFC 2821 and there are many email domains that are aliases where the > mailbox address is expected to remain unmangled by CNAME expansion of > the domain part. The operators of the sending system are stuck in the > distant past.
Thanks Viktor. Yes, I see section 3.6 now explicitly allows "CNAME RRs whose targets can be resolved, in turn, to MX or A RRs", which was the case in my situation. Good to know that Postfix does it better! Michael
