I've been beating my head against a wall for a few days now. The Alphabet company keeps rejecting my emails from the second domain; while the other big players are sending my emails to the spam bin. So, I am curious if anyone has written an 5th grade level script kiddie (5th Grade) level guide to setting up multiple domain emails from a single IP using ISPConfig? I've searched the inter-webs and this forum and my search-fu is coming up short. Thanks in advance.
Never-mind, I figured it out (9th grade level). Figures that it would happen almost immediately after posting this in frustration. It's really simple. Inside ISPConfig create the DKIM, SPF, DMARC (not sure if PTR is needed but I did it, you dig it?). Keep those records in ISP Config and then copy each one, one by one, over to your DNS Registrar. There maybe some slight adjustments to be made depending upon your registrar. Keep the records for mail.domain2.com completely separate from mail.domain1.com. I am guessing that you have to repeat this process for each domain. Also, ISPConfig will complain via email if you don't setup IPv6, so go ahead and setup IPv6/AAAA records. I'm guessing that by doing this at the DNS Registrar level we are confusing the DNS lookups to reveal only the records that are requested versus all that are available on that server. Life is good, thanks for stopping by.
Glad to hear that you were able to solve it, just a few points if someone else reads this as the way you did it may cause you trouble in future as you added DNS records in ISPConfig that should not be there unless your ISPConfig system is primary DNS server. No need to create these DNS records in ISPConfig when the authoritative DNS server is not your ISPConfig server, you should not even create them in ISPConfig as this might cause issues when there are differences between the records in ISPConfig and your real DNS system. But you must create these records in your external DNS system to be able to send emails to Gmail and co. See here for a step-by-setp guide: https://www.howtoforge.com/ispconfig-email-account/ So what you do is: 1) Add the email domain, save it. 2) Go back to the email domain, enable DKIM and create a DKIM key. Copy the DKIN DNS record that is shown as an example as you need that for your external ISP. 3) Create DKIM and SPF record at your external ISP, do not create them in ISPConfig unless your ISPConfig DNS server is your primary DNS server. That's all. ISPConfig does not complain when you have no IPv6 record, ISPConfig does not care at all if you use IPv4, IPv6 or both. I do not use IPV6 on any of my ISPConfig mail servers. But what matters for e.g. Google (and not ISPConfig) is that when you have IPv6 configured for this system in the network config files of your servers, then you must have proper IPv6 records as Google is not able to verify your system hostname without that and will reject emails.
