With the minimal detail of your initial post, there are a couple of options. Nupoint VM has the capability to be up to a 6-port fax server. Using the Unified Messaging capabilities, you can get faxes into mailboxes, then the UM can send them out to users. Information on Nupoint is available on edocs.mitel.com. If you have just a few users, you can do that or even look at online options, like Efax or GFI Online. If you have a LOT of users and/or faxes, you'll need to go to a third-party solution.
I've used GFI fax-server successfully before, but let's not turn this into a fax forum debating GFI, Rightfax, etc. You can do your own research on those, and what matches your company's needs.
It may be a cost issue, but consider running the PRI directly into a fax-board on the fax-server hardware itself. Eliminating any transition through the 3300 may reduce fax errors, as I've experienced before. Also, you're not paying for a Digital Link license on the 3300, but you are paying for a fax-board (e.g., Dialogic-Brooktrout).
Lots of options, but it all starts with how many users you'll have using how many fax numbers with how many incoming/outgoing faxes, particularly simultaneously filling up ports and trunks. Good luck...