What is the best software combination to get email attachments wirelessly?

Boss is using a Treo 650, currently using Verizon's Wireless Sync. Wireless Outlook syncronization is working fine (using PC Monitor), but we'd like to get attachments (500 MB SD card).

I looked at the Documents To Go website, but I'm not sure what product to get.

We have the ability to use Active Sync, if that helps.

Please let me know what's working for you.