Update: Scale improvements have been rolled out for Office 365 announced in 10x increase in Public Folder limits.

It has been about two months since I was in Austin at my first Microsoft Exchange Conference. I must say Austin left quite an impression on me, partly because of the wonderful people and great music, but mostly because of the immensely passionate public folder customers I got a chance to meet. Public folders are one of the oldest living artifacts in Exchange Server and MEC was a reconfirmation that they continue to serve some critical and unique collaboration scenarios for our customers. MEC allowed me to meet with some of our largest and most complex public folder customers to discuss in great detail how some companies’ entire business processes rely on public folders.

At MEC, customers asked us for higher scale and more functionality in Exchange modern public folders. The 3 top asks in the order of priority for the public folder team included:

  1. Scale improvements
  2. OWA support for calendar and contacts
  3. Better public folder reporting tools

What's new on scale?

As discussed at MEC, scaling up modern public folders is a priority for us. We have already made significant strides towards improving public folder scale. We have removed the design limitation which was the root cause for the hard limit of 10,000 total folders - this opens up new doors for scale. Synchronization of public folder hierarchy was a major component responsible for the 10,000 folder limitation. Full hierarchy sync has been improved to the point where it can scale linearly as folder count grows within the environment. There have also been storage optimizations which will provide better performance in operations on public folders in run state.

What does this mean for public folder counts?

The good news is that with these recent changes you can expect to see higher limits on public folders rolled out in the next few months. Office 365 customers should see the total folder limit increase to 100,000by early July. For our large on premises customers, we are targeting to increase this limit further with the CU6 release. As we get closer to the CU6 date we will publish an update on how far we were able to push the limit for on premises customers.

This is just the first round in the public folder scale improvements we are working to deliver. As we move forward with these improvements, our goal is to scale to at least 1 million folders. We are also looking into making improvements to migration as well as store more bytes in more public folder mailboxes with more users accessing them.

Why CU6?

Scale updates is complex business. Investigating and working through fixes on scale required a significant lead time and these updates didn’t fit into the CU5 timeline as work from multiple teams with features dependent on each other were involved. So we plan to roll in the above mentioned scale improvements in CU6 for our on-premises customers. Office 365 customers however will see these updates as soon as the code containing all of the necessary public folder scale improvements rolls out into service. This service update is targeted for early July, but as with all Office 365 updates some tenants will see it sooner than others until the service update has been deployed world-wide. We will be publishing another blog around the CU6 timeframe to share news about the next round of public folder scale updates.

What about the other asks?

We expect calendar and contact public folders support in OWA to follow the scale updates. We do not have exact timelines on these yet. Following calendar & contact folder support in OWA we will be working to deliver additional management tooling to assist in your management of public folders. Stay tuned for updates.

At Exchange we live to solve tough problems. Public folders were re-architected in Exchange 2013 to take advantage of the well proven mailbox design and deliver a solution for customers moving to Office 365 with public folders. We will continue building towards this promise as we proceed to meet customer requirements. Thanks to the customers who provided input at MEC.  We will keep you updated with further details in advance on the Exchange Blog.

Kanika Ramji
Program Manager, Exchange Public Folders