GMX and SPF

So, I finally ran into my first rejected mail due to SPF:

mail:
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
B79A65361      1886 Sat Mar  4 16:20:14  bbeck@lostentry.org
(host mx0.gmx.net[213.165.64.100] said: 550-5.7.1 {mx020} The recipient does not 
accept mails from 'lostentry.org' over foreign mailservers. 
550-5.7.1 According to the domain's SPF record your host '216.27.180.188' is not 
a designated sender. 550 5.7.1 ( http://www.gmx.net/serverrules ) (in reply to RCPT TO command))
                                         Dino-@ist-einmalig.de

lostentry.org is still hosted on SpeakEasy's DNS servers (I didn't get around yet to change that to ns.goodcoffee.net and run secondary on ns1/2.rollernet.us).
SpeakEasy doesn't expose SPF records to their DNS customers. According to check-auth@verifier.port25.com the SPF record

v=spf1 ip4:216.254.0.0/24 ip4:69.17.110.0/24 ip4:69.17.116.0/24 ip4:69.17.117.0/24 mx ptr ~all

as published by SpeakEasy results in a "softfail" condition for SPF. In other words GMX refuses mail on softfail. Niiiice...

The remedy is easy:
Add relayhost=[mail.speakeasy.net] in /etc/postfix/main.cf, restart postfix, done.