SPF records were deprecated in 2014 and TXT records are taken their place to show authorized E-mail servers for a domain. If you run your email domain against both www.kitterman.com
and mxtoolbox.com, both will show errors if your domain uses SPF records in DNS.
I cannot find anything about the syntax for the TXT records they are looking for either Amazons Route 53 and other generic DNS servers.
Can you help?