The MX record will read mail.cruzanLTD.com IP=24.73.160.163 The PTR record is still going to point to mail.todhunter.com
I know, previously, it was stated that the ptr record just has to exist
Best practice is that PTR hostname, the HELO hostname, and SMTP greeting domain name should all be the same, and are more related to the machine's canonical identity, "default hostname", than to any sender/recipient domain SMTP traffic emitted from/received by that machine.
eg:
D.C.B.A.in-addr.arpa. PTR label.domain.com.
... is matched by:
label.domain.com. A A.B.C.D
And then, when the MTA at IP A.B.C.D sends mail, it should send this command:
EHLO label.domain.com
... which identifies the canonical domain name for the machine (and has nothing to do with any envelope sender/recipient domain, virtuals, etc).
When the MTA at IP A.B.C.D receives mail, it should greet with:
220 label.domain.com
Again, label.domain.com has nothing to do with any @recipient.domains that the IP will accept mail for, nor with any MX records.
but doesnt really have to point back to the same hostname as the MX.
no, MX hostnames have nothing to with any other domain names.
The MX hostname tells senders noting more that where to send mail for @recipient.domain. Envelope sender/recipient domains exchange with an IP are not tied or dependent on that IP+s MX/helo/SMTP greeting domain names. This dissociation is obviously required in your specific situation of an IP that will be SMTP sender/recipient for any number of envelope domains.
The best practices for MX hostname is that it MUST have an A record and SHOULD have an MX record.
mxhost.domain.com. A ip.ad.re.ss mxhost.domain.com. MX mxhost.domain.com.
So, ANY @recipient.domain can use mxhost.domain.com as its MX hostname.
recipient.domain. MX 10 mxhost.domain.com.
so in your case:
virtual.domain. MX 10 mail.todhunter.com.
You're thinking there is an MX-hostname-to-PTR-hostname requirement, when there isn't.
And, more that one PTR record for an IP is useless and could cause errors or indeterminate results, since many apps that query for PTR records read only the first PTR record in a response containing multiple PTR records, but you can't control which PTR record of multiple PTR records will be physically first in a DNS answer.
In Imail terms, setting up IMail virtual domains and their MX records has nothing to do with PTR domain name for the Imail IP nor with Imail's HELO hostname.
Len
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