This article introduces the detailed DNS records on a email domain for sending and receiving emails.

Add an A or CNAME record for mail.example.com that points to the IP address of the Webmail interface. This will allow users of that domain to access webmail by typing http://mail.example.com or http://mail.example.com:9998 in their Web browser (depending on whether you use IIS or the included Web server).

Some large email providers like Hotmail and AOL are starting to require specially formatted TXT records to be added to your DNS server. This special format is known as SPF (Sender Policy Framework). Information about how these records should be formatted can be found at Dmarcian. Please keep in mind that the owners of the domains may have significant input on what goes into these records.

Details: https://portal.smartertools.com/kb/a3502/spf-in-simple-terms.aspx?KBSearchID=900982

An important part of the email delivery system is “MX” records. MX records essentially tell the world what server to send mail to for a particular domain name. Priority field: The priority preference for that MX record. MX records are processed in order starting with the one with the lowest priority value and working towards high priority records. In situations where you have multiple email servers, or backup email servers, set a lower priority value for your primary mail server and a higher priority value for your backup server.

Record field: You can specify a 3rd level mail domain here, but typically you will want to leave it as “@” to specify the record is for the root domain name.

Address field: The address of the target mail server. It is recommended to use a domain name value here as opposed to an IP address. Typically you would first create an “A” record of “mail” pointing to the IP address of your mail server, and specify “mail.domain.com” here as the address entry for the MX record. Example MX records: Priority: 10 Record: @ Address: mail.domain.com Priority: 20 Record: @ Address: mail2.domain.com

PTR records resolve IP addresses into hostnames. By setting up a PTR record, the receiving server can do a reverse DNS lookup to verify the sender.

Domain-based Message Authentication, Reporting & Conformance (DMARC) is the latest form of email authentication. It makes sure that legitimate email authenticates against 2 DNS record types: DKIM and SPF.  Also, it ensures that fraudulent email that tries to look legitimate gets blocked.

Details: https://portal.smartertools.com/kb/a3501/dmarc-in-simple-terms.aspx?KBSearchID=900981

Mail signing protocols, such as DomainKeys and DKIM signing, verify the authenticity of a message and can be used to protect users from phishing schemes or spam attacks. 

Please refer to the article https://portal.databasemart.com/kb/a266/how-to-configure-rdns.aspx to add PTR record for email server. Please use a valid email domain name as the value of PTR record.

The DKIM key is generated from email server.

After generating the key, please refer to the step 2 and three of the above article to add DNS records for DMARC and DKIM.