test_mailer.text_body_template I noticed the following text:
Note that you need to enter both SPF and TXT versions of this record for maximum compatibility.
AFAIK this is wrong. Only the TXT RR should be used. See RFC 7208 (section 3.1) for more details.
And here is what the Wikipedia entry has to say about this:
Current practice require the use of TXT records, just as early implementations did. For a while a new record type (SPF, type 99) was registered and made available in common DNS software. Use of TXT records for SPF was intended as a transitional mechanism at the time.
The experimental RFC, RFC 4408, section 3.1.1, suggested “An SPF-compliant domain name SHOULD have SPF records of both RR types”. The proposed standard, RFC 7208, says “Use of alternative DNS RR types was supported in SPF’s experimental phase but has been discontinued”.
I suggest we remove this note since it is wrong and will only confuse people.