Ok a little preface, Ive been running multiple servers for like 10 years with email working successfully for many customers/domain all on 1 IP address. I, no doubt, still have way more to learn but again stuff has been working for years so that makes me think I’ve done something right, but to the current issue:
customer cant add their email account to 3rd party email apps (tried outlook and apple mail) by using their own hostname, they must use the main server hostname for it to work. I believe customers could use their own “mail.theirdomain.com” previously but honestly I could be misremembering.
reverse DNS only returns the main hostname for their domain. Is it even possible to have each domain return their own revers DNS or does this require unique IPs?
If I jumped to unique IPS for each customer using the same server (I assume that’s possible and what a pro would do) is it worth the effort and is there any functionality or security issue with how Ive been doing it all these years if I continue as is?
I presume you mean a email client like thunderbird. This should not be a issue. Virtualmin sets up auto config and all the customer needs to do is get the email and password correct. (unless the autoconfig is sending the incorrect details)
Adding there own domain name for mail server is pretty standard setup.
Maybe the customer has done a few fails and there IP has been add to fail2ban.
Also it not hard to add full system info, just a matter of copy paste from virtualmin.
Any name that gets resolved to that IP address should work unless something strange has happened. The server listens on ports for certain traffic. Does mail.theirdomain.com exist in the DNS records? Did you do anything to the templates?
No, it is not possible (or, rather, it violates the spec to do so). How could it be? There is only one IP and it needs to point to the canonical name for that host.
You should stop caring, though. PTR doesn’t matter. I mean, you need a PTR, it needs to resolve both ways, but it doesn’t matter what it is. Google and Microsoft don’t use their customer names for their PTR records (or the MX records, for that matter). This is all stuff below the level of user awareness, and you’re just wasting time trying to obfuscate the path mail is taking.
I believe you can configure particular domains mail to be sent from a particular IP if your server has more than one. Each of those IP could have their own rDNS but the servers host name would only use one.
My servers hostname matches it’s rDNS and I only have 1 IP.
Joes post above is correct and he knows enough of this stuff.
and he knows enough of this stuff.