Sender Policy Framework(SPF DNS)
A Sender Policy Framework(SPF) is a way to explicitly define which mail servers are allowed to send email for your domain name. SPF records are very easy to create and can solve a number of issues regarding sending email.
SPF records are simply TXT records placed into a domains DNS zone file. Your basic SPF record may look like the following:
@ IN TXT “v=spf1 a mx -all”
- v=spf1 – defines this is an SPF record
- a – allows the A record to send email
- mx – allows the MX record to send email
- -all – specifies that all emails sent through a different mail server will return a code of “hardfail”. The email will NOT be delivered, instead generating a bounceback email. If you would like to force a “softfail” and allow email sent through a different mail server to be delivered, change the “-all” to “~all” and the email will be tagged as “suspect” and delivered to the recipient.
In order to specify other mail servers that are allowed to send email for your domain, you would add the domain to the SPF record as follows:
sampledomain.com IN TXT “v=spf1 a mx a:mail2.sampledomain.com -all”
In HELM, go to your domain names “DNS Zone Editor”. Create a new record type “TXT” with the record name “@” and place the SPF into the record data field.