There are 2 other ways I have used in the past. Either create a valid Bugzilla XML document and import it with importxml.pl http://www.bugzilla.org/docs/tip/en/html/api/importxml.html
Or use email_in.pl http://www.bugzilla.org/docs/tip/en/html/api/email_in.html
Bugzilla XML allows you to specify a lot of details, but is more complicated. Using email_in.pl only allows you to import a subset of the fields, but it may be sufficient and is much easier.