service/email.md

@@ -353,6 +353,14 @@ and reverse IP configuration and reply with a report by email.
 
 Interestingly, ran by [sparkpost](https://www.sparkpost.com/).
 
+### Other SPF validators
+
+Those services also provide ways to validate SPF records:
+
+ * <https://www.kitterman.com/spf/validate.html> - by a Debian
+   developer
+ * [pyspf](https://pypi.org/project/pyspf/): a Python library and binary to test SPF records
+
 ### Testing the submission server
 
 The above applies if you're sending mail from an existing TPA-managed