I am using PHPList to send emails to my subscribers. When you use PHPList (or any other self-hosted email programme) a large number of mails are either rejected outright or delivered to the Spam/ Junk folder of the recipient.

Three things are essential to avoid emails being rejected by the receiving or being treated as SPAM:

(i) Reverse DNS
(ii) SPF Record
(iii) DomainKeys Identified Mail (DKIM)

In Hotmail, even if you add the sender to the contacts, the message sent without SPF Pass & DKIM will carry a warning flag that the sender has failed Hotmail’s fraud check.

If you look at your messages that are undelivered or rejected, the reason is very blunt:

Diagnostic-Code: SMTP; 421 Refused. You have no reverse DNS entry.

or

(reason: 450-4.7.1 Client host rejected: cannot find your reverse hostname, [IP Address])

or

Our inbound servers require reverse hostname for the sender server to be present in order to accept the email. You need to contact the reverse hostname's email admin to add the rDNS to into his server.

Setting the Reverse DNS is very easy if you have SolusVM Control Panel.

First, set your hostname (this actually should be done at the very first stage of setting up the VPS, especially if you are installing email) in the box available in the home page of the Control Panel.

Check that the hostname is correctly set by entering the following commands in the Putty terminal:

hostname
hostname -f

Now, find the Reverse DNS box under the Network Tab and enter the hostname and click the Edit button.

Now the system will generate the Reverse DNS at it will take upto 24 hours for it to be propagated throughout the Internet.

You can check whether the Reverse DNS is properly set by going to dnsvalidation.com. If all is OK, you will get the message:

Reverse Entries for MX records

pass

OK. All MX records have reverse DNS entries. All mail servers should have a reverse DNS (PTR) entry for each IP address (RFC 1912). Missing reverse DNS entries will make many mail servers to reject your e-mails or mark them as SPAM.

Reverse DNS Entries Resolves

pass

OK. All reverse DNS entries resolves. All IP’s reverse DNS entries should resolve back to IP address (MX record’s name -> IP -> IP Reverse -> IP). Many mail servers are configured to reject e-mails from IPs with inconsistent reverse DNS configuration.

If you have VePortal, then you will have to open a support ticket for your webhost to do the Reverse DNS.

How To Set Reverse DNS for VPS IP Addresses

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