Destination mail server blocking Blackberry-sent mail due to SPF requirements

I have a problem getting mail to go to a certain domain when sent from a blackberry.  The receiving server indicates it cannot resolve an SPF record.  I need help in isolating the problem.

Sender is a blackberry using blackberry's SMTP server.
Return email address is SendingDomain.com which resides on my Exchange Server.
Target email address is TargetDomain.com, which also resides on my Exchange Server.

The target email address is a "forwarder account", which basically bounces the TargetDomain.com email address to an SMTP address outside of my network.  Mail to target domain is not stored on my Exchange Server.

We can send email all day using a variety of clients.

However, when sent from the blackberry service, I get this message:
[Target User Account] on Thu, 6 Sep 2007 09:15:43 -0500      There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.      <gipper.beprominent.com #5.5.0 smtp;550 68.216.179.6 does not pass SPF requirements for domain srs0=rpj8tl=oc=[SendingDomain].com=roger@srs.bis.na.blackberry.com>

I have created an SPF record for [SendingDomain].com on our Windows DNS server as follows:
v=spf1 a:mail-server.beprominent.com a:gipper.beprominent.com a:srs.bis.na.blackberry.com mx:blackberry.com include:blackberry.com ?all

Thanks in advance...
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