cannot add email domain for email to fax feature

we are trying to add the ability for all users in our email domain to be able to utilize the email to fax feature. we can only add individual emails under each number, we have over 900 users with emails. that is not going to work. i need to find out how to enable this on the acct. i see where we can add up to 25 users per number, that just will not work. also there is a external communications area and we added our domain to it, but after testing no faxes will go through. ive opened a case and now 2 days later its never been touched. if my plan doesnt allow for this i need to know the plan that does and how i can move to it.