After reviewing the docs for this module as well as reviews and the bug list it would appear this module does not work and has not worked in sometime. The description listed in the documentation reads as follows.

DESCRIPTION

Because Gmail is currently in Beta testing, expect this module to break as they make updates to thier interface. I will attempt to keep this module in line with the changes they make, but, if after updating to the newest version of this module, the feature that you require still doesn't work, please contact me with the issue.

Given that the module is close to 5 years old and gmail has undergone many updates it seems unlikely that this would work. You would probably have more success using pop3 or imap. Good Luck