The SPF record is a TXT record that is defined in the DNS zone of a given domain. It is used by receiving mail servers to check if the mail comes from an SMTP server authorized to send it. It is therefore important to set it and set it correctly so that the emails sent do not end up being marked as spam by the receiving servers.
By default for each of our hosting the following SPF record is defined:
v=spf1 mx a ptr include:_spf.servers.li ~all
How to add other custom servers
Let's say your company sends mail through an internal mail server. In this case, this mail server must be added to this SPF record. Otherwise sending from this server the SPF check will fail and your mails will be exchanged as spam. Let us assume in this example that your server has as IPv4 address 1.2.3.4 and as IPv6 2001: db8: 3333: 4444: 5555: 6666:1.2.3.4 in this case to the record above you will have to add:
ip4:1.2.3.4 ip6:2001:db8:3333:4444:5555:6666:1.2.3.4
therefore the complete updated record will be:
v=spf1 mx a ptr ip4:1.2.3.4 ip6:2001:db8:3333:4444:5555:6666:1.2.3.4 include:_spf.servers.li ~all
SPF record syntax check
If you modify the SPF record, you need to make sure that the syntax is valid. To do this you can use the following online tool:
https://www.kitterman.com/spf/validate.html
you simply need to enter your domain on this page and the tool will verify the validity of your SPF record for you.
