There are situations where you wish to add more than one IP address to your SPF Record.
A standard SPF syntax looks like below:
v=spf1 include:example.com -all
In the above example, only example.com is allowed to send email. If you have your email in Outlook it would look something like this:
v=spf1 ip4:123.XX.XXX.12 include:spf.protection.outlook.com ~all
In the above example, outlook.com is allowed to send emails as well as an ip 123.XX.XXX.12
If you want two IPs to be allowed, just add another IP next to the existing line. For example:
v=spf1 ip4:123.XX.XXX.12 ip4:456.XX.XXX.34 include:spf.protection.outlook.com ~all
This allows two IPs. You can add more IPs in the similar fashion in your SPF Record.