Using SPF record restrict the hosts allowed to send message on your behalf. If you are using Blackberry device, all your e-mail are relayed through RIM servers. So to make delivery successful, you need to allow their servers.
Add the following to your DNS text string to allow RIM servers to send out e-mails with your domain:
"v=spf1 a include:srs.bis.na.blackberry.com include:srs.bis.eu.blackberry.com ~all"