I wanted to know the best way to make my mailserver send emails on behalf of my clients' domains, without being greylisted and also avoiding bounce problems.
HELO mymailserver.com MAIL FROM<email@example.com> # mymailserver.com same IP as myapp.com DATA From: <firstname.lastname@example.org> Sender: <email@example.com>
Question: This is what gmail does. It's the msg header "From:" that has a different domain, not the envelope sender.
emailclients will show "From:firstname.lastname@example.org via email@example.com" or "From:firstname.lastname@example.org On Behalf Of email@example.com", which is not a problem for me.
Now, will this affect badly the reputation of my domain, the fact that the header "From:" has a different domain? (and if it's not Google who's doing it..)
HELO mymailserver.com MAIL FROM<firstname.lastname@example.org> DATA From: <email@example.com> # same as A, but no "Sender:"
It looks like Google once did this and called it a mistake
A bug removed the "Sender:" from their messages and the "via" didn't show up in the emailclient. (The RFC says that it MUST be present if it's not the same as the "From:")
HELO mymailserver.com MAIL FROM<firstname.lastname@example.org> DATA From: <email@example.com>
It's as if client.com were sending the message (the MAIL FROM is "spoofed" too). But if the client.com domain is well-known or has a SPF entry in its DNS, I would have to alter its DNS, allowing mymailserver.com to send message in their behalf.. (This is impossible for me because of the nb. of clients, and also some of my clients don't have control over their domains, i.e., are using @gmail.com themselves)
HELO mymailserver.com MAIL FROM<firstname.lastname@example.org> DATA From: <email@example.com> Reply-to: <firstname.lastname@example.org>
Question: This is the simplest one, I would only add a "Reply-to:" header. Is this really taken into account ALL THE TIME by email clients? Can this be perceived as spoof too, adding different domains to the "Reply-to" header, and be a bad influence to my domain's reputation?
- The RFC only says that "if the Reply-To field exists, then the reply SHOULD go to the addresses indicated in that field and not to the address(es) indicated in the From field.".
- Only the "From:" header label would be "spoofed":
"From: myclient.com (via myapp.com) < email@example.com> ".