Reverse DNS

#1
Hi,
We just signed up for a VPS and everything looks great except the reverse DNS on domains with dedicated IP’s. I'm not too clear on how this all works and if someone can advise me what needs to be done I would be forever grateful.

Here’s the scoop;
the hostname on the vps was changed (svr1.serverdomain.com), RDNS was setup and everything is fine on that end. All domains without a dedicated IP work fine.

But, when I added a domain with a dedicated IP (domain2.com), dnsreport said: FAIL - Reverse DNS entries for MX records. So I contact support to setup RDNS and now the FAIL is fixed but when you run a tracerout the hostname is the same as the domain name IE, "domain2.com".

Every reseller account I’ve had/have uses the server hostname , IE, “svr1.serverdomain.com”, even for domains with dedicated IP’s.

Can RDNS be setup up for the server hostname even though it’s a different IP?

Anyone have any idea what I, or support needs to do to set this up right? On our reseller account I can add a domain with a dedi IP and it just works with no FAILS.

Being a managed VPS I thought this would all be setup to work. I’m not a server admin which is why I opted for a managed solution.

Any help or advice on this matter would be greatly appreciated.

Thank You
James
 

KH-Paul

CTO
Staff member
#3
James,

The only IP that really needs a PTR record to be setup is the primary IP of the system. PTR records are used by some mail servers to verify identity of the source system and as mail is being sent through the primary IP of the VPS only that IP requires a valid PTR record which should match with VPS hostname (or better say with the name used by your mailserver as an argument for the HELO/EHLO SMTP command). Presence or absence of the PTR record for non-primary IP won't affect any functionality and/or performance in default configuration. In other words PTR records for non-primary IPs is nothing but some sort of a "fancy" thing.
On a side note - the way how your reseller account is configured isn't correct as forward and reverse resolution won't match.

And regarding dnsreport - the failure that you're seeing there is misleading as dnsreport has no knowledge of your system configuration and what IP is configured as primary IP there, how mail server config is built, etc. The correct way to get rid of that failure is to change MX record for the domain configured on non-primary IP to point to the name that resolves to the primary IP of the system. In case of cPanel/WHM VPS you can do the following to change MX record:
1. Go to WHM >> DNS Functions >> Edit DNS Zone >> domain.com
2. Change value of the "MX" record from domain.com to mx.domain.com
3. Scroll down to the section where you can add new records and create the following "A" record:
mx 14400 IN A primary-ip-of-your-VPS
4. Click Save and re-check dnsreport.

Regards,
Paul
 
#4
Oh, I get what you're asking for now.

If you just want the MX records to pass for every domain you create then it's easiest to edit WHM's standard zone file template to insert the primary hostname (or whatever that IP will resolve to) rather than dynamically expanding mail.%domain% as it sees fit. If you've already created domains you want to change then those will have to be altered one-by-one as outlined above.

This is busywork for the most part, but there are some mail servers out there who will refuse you if the names don't match. One of my clients had this problem with a server at UNM in Albuquerque.
 
#5
Thank you Paul, that cleared a few thing up. And thanks for all the help you've provided via helpdesk.

And thank you khiltd.
some mail servers out there who will refuse you if the names don't match.
If which names don't match? The domain name and the hostname?

Thanks

Knownhost support is fantastic!
 
#6
If which names don't match? The domain name and the hostname?
If the sending IP does not resolve to the same name the MTA advertises when it sends the HELO command then some especially finicky servers will silently fail the connection, leading to people wondering why no one is receiving their email.
 
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