The SPF project provides an SPF verification tool. Send an email to spf-test@openspf.org and you will receive results via an SMTP time rejection. You will get results either in your MTA mail logs or via however your MTA reports errors to message senders (e.g. a bounce message). This is done to avoid the risk of backscatter from the tester. This test tests both MAIL FROM and HELO and provides results for both.
It uses the Python SPF (pySPF) library. This library is fully compliant with the SPF specification and passes all the tests in the SPF test suite. MTA services for this test are provided by Controlled Mail.