Route53 and some other providers have limits on the size of a TXT record in their DNS control panels. These limitations are smaller than the RFC specified limits and may cause issues is you are trying to use our manual SPF process. 

This document provides and example of how to split up your SPF TXT records to fit in Route 53 and it may work with other providers. 

https://salferrarello.com/dkim-route53-characterstringtoolong-value-is-too-long/

Alternatively you can use our automation SPF flattening with does not have this same issue.