tester for spf and dkim

RealSender offers a free online check tool
to validate your SPF + DKIM settings sending an email message:

1. send an email to spf@tester.realsender.com
2. check online the SPF validation results at tester.realsender.com/spf
   (it will take a minute to appear)

During verification, a prefix is added to the subject
if the message is not authenticated correctly.

Details on how it works
are located in the “email authentication basics” area of the website:
email authentication basics :: <spf> check online