This technology helps to prevent eMail envelope forgery.  (Technical note:  The SPF mechanism applies to the sender's eMail address as it's presented in the "MAIL FROM:" command during the SMTP envelope stage; it does not operate on the "From:" SMTP header that is normally presented on-screen along with each eMail message.)

The SPF checking tool is available, here:  https://www.openspf.ca/why.perl

More tools are available in the "Tools" section of this web site, including...

SPF analysis

Aanalyze the configuration of SPF records for any domain and generate a detailed report.

SPF "Why?" test

Check the SPF configuration of your mail servers to confirm whether you can send eMail.

The Lumber Cartel
local 42 (Canadian branch)
RBL check, WHOIS lookup, Ping, and other various online tools.