Send Email from Dedicated IP with rDNS

EneTar

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Dec 19, 2015
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I have "Send mail from the account’s IP address" enabled at WHM -> Exim configuration. I also have assigned a for a few websites dedicated IPs. (Every user has its own) Should I set the Reverse DNS for each IP pointing to the domain of the user? Will it help with email deliverability?

In How to Keep your Email Out of the Spam Folder - cPanel Knowledge Base - cPanel Documentation it states
If you have configured Exim to use a different IP address, ensure that the PTR record of that IP address uses the hostname of your server.
What if a user has 2 domains a primary and an addon? Where should the rDNS point out?
 

GOT

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EneTar

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Dec 19, 2015
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From How to Configure the Exim Outgoing IP Address - cPanel Knowledge Base - cPanel Documentation if "Send mail from the account’s IP address" is enabled it overrides any manual changes at /etc/mailhelo and /etc/mailips. I want to have this option enabled so that each user's email is routed through it's own IP.

The same page says:
To automatically configure Exim to send mail from each domain's dedicated IPv4 address, ... Modify the rDNS for each IPv4 address to point to the desired domain.
So assuming example.com has a dedicated ip address xx.yy.zz.ww should I set the rDNS as example.com? or something like mail.example.com ? If I point the rDNS at example.com. then MXToolbox complaints that the rDNS is not a valid hostname
 

cPanelMichael

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Apr 11, 2011
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Hello @EneTar,

It's generally advised to configure the RDNS record of the IP address used to send email to the server's hostname. However, if you have configured Exim to send email from a domain's dedicated IP address, ensure the RDNS records for the dedicated IP address point to the individual domain name (e.g. domain.tld and not host.name.tld or mail.domain.tld).

The MXToolBox warning is likely a false positive.

Thank you.
 

EneTar

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Dec 19, 2015
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1) Shouldn't the RDNS be a valid hostname meaning a FQDN? domain.tld is not a FQDN but host.domain.tld or www.domain.tld or mail.domain.tld seem to be FQDNs.

2) Is there any advantage using domain.tld as you suggest for rDNS instead of mail.domain.tld?

3) Moreover what about the addon domains on accounts with dedicated IPs? Where should the rDNS point out? I guess at the primary domain. But what does this mean for the email deliverability of the addon domain?
 

cPanelMichael

Administrator
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Apr 11, 2011
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Hello,

I recommend voting and adding feedback to the following feature request if you'd like to see an improved method of defining the HELO name for outgoing email:

An option to use actual reverse DNS resolution as HELO for outbound email.

1) Shouldn't the RDNS be a valid hostname meaning a FQDN? domain.tld is not a FQDN but host.domain.tld or www.domain.tld or mail.domain.tld seem to be FQDNs.
The server's hostname should be a fully qualified domain name (e.g. server.domain.tld), but the RDNS entry for a domain's dedicated IP address can be "domain.tld" as long as it's the only domain using that dedicated IP address for sending email.

2) Is there any advantage using domain.tld as you suggest for rDNS instead of mail.domain.tld?
The RDNS entry for the domain's dedicated IP address should match the domain name utilized in the /etc/mailhelo file.

3) Moreover what about the addon domains on accounts with dedicated IPs? Where should the rDNS point out? I guess at the primary domain. But what does this mean for the email deliverability of the addon domain?
If an account with a dedicated IP address sends email from multiple domains, then enabling the Send mail from account's dedicated IP address option is not recommended.

Thank you.