I implemented an SPF record for our domain and was testing this out, but kept getting SPF_SOFTFAIL's using perl-Mail-SPF-Query.
Googling around, I found this thread (
The users October 2007 Archive by thread) that suggests that perl-Mail-SPF-Query is abandon-ware, and that you should be using instead perl-Mail-SPF.
After switching to perl-Mail-SPF, everything started working for me, so I've updated the wiki page:
Improving Anti-spam system - Zimbra :: Wiki