123-Reg Email blocked by broken SPF?

Trying to send email to my MP results in fail!

 

mike@penning4hemel.com
 host mx0.123-reg.co.uk [94.136.40.152]
 SMTP error from remote mail server after RCPT TO: mike@penning4hemel.com>:
 550-Callout verification failed:
 550-553-SPF (Sender Policy Framework) domain authentication
 550-553-fail. Refer to the Troubleshooting page at
 550-553-http://www.symanteccloud.com/troubleshooting for more
 550 553 information. (#5.7.1)
Reporting-MTA: dns; relay1.thorcom.net
Action: failed
 Final-Recipient: rfc822;mike@penning4hemel.com
 Status: 5.0.0
 Remote-MTA: dns; mx0.123-reg.co.uk
 Diagnostic-Code: smtp; 550-Callout verification failed:
 550-553-SPF (Sender Policy Framework) domain authentication
 550-553-fail. Refer to the Troubleshooting page at
 550-553-http://www.symanteccloud.com/troubleshooting for more
 550 553 information. (#5.7.1)

This is wroing because:

a) my SPF is setup correctly!!

b) you can’t find help on it in the recommended place: http://www.symanteccloud.com/troubleshooting

ARRRGGGHHH!!!

Come on 123-REG you can do better than this!

Mike Tubby