An SPF record is a type of record attached to a domain that identifies which mail servers are permitted to send email on behalf of said domain. The creation of an SPF String would be made at the domain host level when migrating hosting services to Redtail. If Redtail is providing email hosting service for the domain, the SPF String should be:
v=spf1 ip4:220.127.116.11/27 ip4:18.104.22.168/27 ~all
Below you will find steps that will show you how to verify an SPF String for a domain:
Open your internet browser and navigate to https://mxtoolbox.com/spf.aspx. The URL will take you directly to MXToolbox's SPF Record Lookup tool.
Once the page loads, enter the domain on which you wish to verify the SPF String, followed by hitting Enter or clicking the SPF Record Lookup button to perform the query. Below is a sample of the query results. As you can see below, the Value field lists both ip ranges (22.214.171.124/27, 126.96.36.199/27) within our SPF String. If this information is not displayed, then the domain does not have Redtail SPF information attached to it.