This is what documented in the Exchange 2010 SP1 beta Hosting Deployment Help file,
Exchange 2010 SP1 doesn't support the following features in Hosting
- Exchange Management Console
- Unified Messaging Server role
- Business-to-Business features such as cross-premises message tracking and
- Outlook 2003 support (EnableLegacyOutlook)
- Edge Transport Server role
When I look at this and trying to think about what some of the current HMC hosters will think, I believe they will probably say, no big deal except for Public Folder and Outlook 2003 support. 50% and probably more of the HMC hosters that I came across provide Public Folder as part of the deal. Obviously, taking away Public Folder means that Outlook 2003 has to go too because you can't have Outlook 2003 without Public Folder, it just won't work. It also means, you have to provide some form of migration for your customers who currently has access to Public Folder to other solution such as SharePoint. That will definitely make things a little bit more complicated and require more advanced notice and planning. So, might be something to think about as you are doing your planning right now. At the same time, it may not be a bad idea to start planing to encourage your customers to upgrade to Outlook 2007 and above if they haven't done so. I know, I know, it is definitely easy to say than done.
Having to say that, in my humble opinion, Public Folder is definitely worth removing for a number of reasons even though I think some of you might disagree,
- Managing Public Folder quota is a big mess. The only way to manage the quota is to ensure that the public folder is created from a control panel and have the quota appropriately enforced. Too often, this is overlooked. I have met a lot of people who assumed that when you assign a quota of say 100MB to a folder, it will calculate 100MB of size for all the content as well as the content of the sub folders in that folder. Unfortunately, that's not true. Each folder has it's own quota limit and it doesn't inherit the quota from the parent folder. As a result, in order to have a good enforcement of size in public folder, you must not allow your users to create sub folders using Outlook because if you allow that, you will lose control. I have come across many customers who initially offered their customers a 100MB folder but end up hosting over 5GB of data just for that organization.
- Public Folder OAB cannot scale well. Alright, here is a shameless cut and paste from Grahame, 'There is a known problem with Public Folder OABs. Each of these generates a Replid and we have seen that more than approximately 20 000 of these can lead to … A workaround has been developed which allows small organisations to share an OAB (users are not aware it is shared). See <> for details. Note that this limit applies only to PF-based OABs. Hosters expecting to have many thousand hosted organisations should deploy web-based OAB distribution in HMC 4.5.' You can find the the FAQ by Grahame Ash from here, http://blogs.msdn.com/b/mkostersitz/archive/2010/05/03/hmc-4-x-faq-by-grahame-ash-principal-premier-field-engineer.aspx
- No last accessed date for Public Folder. There is no attribute in each of the item in the Public Folder to tell you when was this item last accessed. So, in another word, you don't really know any of those document is active. This is one big weakness of Public Folder. In addition, unlike in SharePoint, you can't have any versioning as well.
I can definitely name a few more but I will stop here. I think it is going to be a slightly painful process to move people away from Public Folder but I still think it is way worth it.