Publishing a Sender Policy Framework (SPF) Record in your domain’s DNS specifies which server IP addresses are allowed to send emails from your domain.

Having a properly set up SPF record makes it less likely that outgoing mail will be tagged as spam.

Return as a TXT Record

Although it appears that best practice is to publish SPF records via DNS as both a SPF and TXT record, the DNS management utilities for some hosts only provide for the addition of txt records

For a good description of SPF as TXT records, see here.

SPF Generators

From the MS Generator: v=spf1 a mx ip4:123.45.678.90 mx:mail.yourdomain.com -all

Add text record with -all amended to ~all, which allows a ‘soft fail’:

v=spf1 a mx ip4:123.45.678.90 mx:mail.yourdomain.com ~all

This assumes that there is also an mx record for a mailserver for the domain in question.

Check SPF Record

Use this tool to check SPF records on your domain.

Resources

• https://www.digitalocean.com/community/tutorials/how-to-use-an-spf-record-to-prevent-spoofing-improve-e-mail-reliability
• SPF Wizard
• MS SPF Wizard
• Reverse DNS from command line
• Reverse DNS on Linode
• Useful article on reverse DNS