Since SPF records are DNS TXT records, they can only contain up to 255 characters of information. In some situations, you might not be able to fit all your sending networks in a small, 255-character text string.
So, what do you do?
Easy! Just use SPF's "include" functionality to link multiple SPF records together. Click on the string below to see the dnsstuff.com SPF lookup for a example domain:
Processing SPF string: v=spf1 include:spf-dc1.digitalriver.com include:spf-dc2.digitalriver.com include:spf-dc3.digitalriver.com include:spf-dc7.digitalriver.com include:spf-dc5.digitalriver.com include:spf-dc6.digitalriver.com ~all.
Notice where it says "include:xxxx1.domain.com"? That's instructing the SPF resolver to also look up the SPF record for xxxx1.domain.com and include it as part of the results for domain.com.
Not only does this help you when your networks won't fit, but it can help you make changes and updates easier.
- Adding a second domain? The second domain's record would only have to contain an "include" statement that references your primary domain. When the primary domain's SPF record is updated, the one for the new domain is also updated, automatically.
- Have multiple facilities on different networks? Utilize the "include" functionality to link to additional facility-specific SPF entries. Then when a single facility's network changes, you only have that one SPF record to update.
