SPF and DKIM will be super easy. Multiple domain support in OpenDKIM is very easy, in particular. I manage outbound mail for multiple domains from my own Postfix server. Ultimately, the tech bits are going to be easy. The harder part is, if you have users, is making sure one of them doesn't spam, impeding the ability for the others to get their mail delivered.
In other words, if customer #1 annoys Comcast and causes a block at 2:30 pm, the next person to try to send mail at 2:45 pm, even if they're not a spammer, is going to see their mail rejected. You'll want to monitor for rejections and be prepared to request unblocking and/or sanction misbehaving customers as needed. Cheers, Al Iverson On Sun, May 3, 2026 at 9:20 AM Marco Moock via mailop <[email protected]> wrote: > > Am 03.05.26 um 04:11 schrieb Miles Fidelman via mailop: > > It's been a while, and what with DKIM & DMARC and all, I've lost track of > > the details. So I wonder if someone might offer some quick advice on > > configuring one server as the outgoing server for multiple domains, all > > behind a single IP. > > Create one SPF record for this server and let all domains point to it. > For DKIM, you can set up opendkim-milter with multiple domains. > > Then set up virtuser-aliases for every domain if needed. Set up relaying > for the existing addresses only if possible to avoid backscatter. > > -- > Gruß > Marco > > Junk-Mail bitte an [email protected] > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop -- Al Iverson // 312-725-0130 // Chicago http://www.spamresource.com // Deliverability http://www.aliverson.com // All about me https://xnnd.com/calendar // Book my calendar _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
