There are four DNS records that affect email delivery:
- The MX record;
- The A record of the subdomain that the MX record points to;
- The SPF record (a TXT record);
- The DKIM record (also a TXT record).
The information that is contained in those records needs to be present in your DNS configuration in order to ensure the proper operation of your email. The records are created automatically on our servers.
You can review the values of these DNS records on the DNS Manager page of the Control Panel of your hosting account.
Records for incoming email
The most important type of DNS record for email is the MX type. MX records determine where email for the domain is going to be delivered. For example, the default MX record on our servers is similar to this:
example.com. 14400 IN MX 0 mail.example.com.
This tells mail servers that email for example.com (for instance, when a message is sent to [email protected]) should be delivered to mail.example.com. It is possible to have more than one MX record; for our servers, this is not necessary.
A record for the mail host
A mail server would then check the A record for mail.example.com:
mail.example.com. 14400 IN A 126.96.36.199
The sending mail server knows to which IP address (188.8.131.52) to deliver the message this way. This IP address will be different for your hosting account, so you should get it from the DNS Manager page of the Control Panel.
Records for outgoing email
Basically, the records above are sufficient for incoming email delivery. However, there are a couple of other records, all implemented as TXT records, that are now widely used to reduce the amount of spam delivered over the Internet. They can help your outgoing email reach its destination without being blocked by spam filters.
The first one is the SPF record. On our servers, the default SPF record looks something like this:
example.com. 14400 IN TXT "v=spf1 a mx include:sXXX.smtp-spf.sureserver.com ~all"
sXXX.smtp-spf.sureserver.com part varies depending on the hosting server your account is on. This record tells other mail servers that legitimate email from example.com may come from the IP addresses that the A and MX records point to, as well as all servers in the SPF record for sXXX.smtp-spf.sureserver.com. This helps other servers detect spam that falsely claims to be sent from your domain.
The other TXT record that is needed for email sent from our servers is the DKIM (DomainKeys Identified Mail) record. Our servers sign outgoing messages using DKIM. This record is defined for the "dkim._domainkey" subdomain, and is similar to this:
dkim._domainkey.example.com. 14400 IN TXT "v=DKIM1; k=rsa; p=1RxyKBp/fDaGUQw2bdMpbe3E9HgBXATjTH/QfSA3dqvjp3QEIM+cjHXwVNQpWp/2aTYCbJ1CADB6Tu/FBI4H03hmtY1Ab3xCMMoGvbqbB+GrgcfYbEI+kGxAJAPUqvQOSs03hIGQA13PLsVOQRCVdMBhwxS6BxjrAuQ1gCqjs/M7KstbABsXxLt4BCGrSY9KpavSQDtDtZNMRgBXvEqImaig"
The DKIM record contains a cryptographic key that lets receiving servers ascertain that the message was indeed sent from your domain.