We have had so many issues with customers and their big mailboxes because EAS is not working past 5 GB mailboxes or if the mailbox has more than 10,000 items.
If SmarterTools could make their own email client that would work with big mailboxes, and have like Exchange/Outlook features as contacts, calendars, notes. Be able to make meeting requests and so on, we would have a winner combination.
Maybe make the client subscription based like MS and we providers buy them in packs of 5,10,25,50,100,200 or whatever makes sense.
There is no good alternative out there to compete with Outlook.