is there any way to make the mailforward sending domain the domain of the mailforward's source address rather than the servers host domain? eg i'm running postfix on ubuntu 18.04, the server hostname is mail.scl.co.uk. if I have a mailforward for eg [email protected] to [email protected] if i send an email to [email protected] from a gmail account, without postsrsd, the mailforward would go out, but still shows as coming from <sendername>@gmail.com, which would fail spf checks, as my server isn't authorised to send mail for gmail.com if the same email is sent, with postsrsd installed, the mailforward shows as coming from srs0=####=##=gmail.com=<sendername>@scl.co.uk is there any way to get this to send out as the mailforward source domain instead of the servers own domain? so for the above example, with postsrsd, the email from gmail.com would be send out from our server as coming from srs0=####=##=gmail.com=<sendername>@scl.net instead of srs0=####=##=gmail.com=<sendername>@scl.co.uk and a mailforward source of [email protected] to [email protected] would go out from our server as coming from srs0=####=##=gmail.com=<sendername>@customersdomain.com not srs0=####=##=gmail.com=<sendername>@scl.co.uk we have a lot of mailforwards, for a lot of different domains, and would prefer them to go out on the mailforwards own domain. I know the servers senderscore will not be affected by this, but I don't want our own domain to be seen as spamming, especially as our customers sign up for all sorts of mess, and we don't want to be seen by gmail/outlook etc as being the originating source domain of that.
We use postsrsd as well, and there's probably not an easy way to do that, though it is an interesting idea. A quick search finds this discussion which sounds like postsrsd wouldn't be the tool for this, due to how it interfaces with postfix. So maybe something like srs-milter, or search for other options. One consideration with forwarding from srs addresses on the customers' domains is the customer must maintain an appropriate SPF record for it to work. Of course that's assumed to happen if the customer already sends from that mail server, but sometimes customers do not do that, they only forward their email to gmail or elsewhere, and never mess with SPF. Not a showstopper issue, just a consideration. With ISPConfig, you must keep in mind that some forwards happen in postfix (mail forwards), and others happen in dovecot (mailbox "send copy to" gets written as a sieve rule, as do rules created by sieve clients). The dovecot "forwards" are actually an entire new email injection into postfix, and couldn't be handled as nicely (eg. I'm thinking handling bounces) as pure postfix forwards. Perhaps it would be worth looking at implementing a mailbox "send copy to" as a postfix-level forward, though sieve forwards will still be around and need considered as well.
