When Planning a Public Folder Migration to Office 365, there are several key components you’ll want to analyze. In this post we’ll cover public folder migration from Exchange 2007/2010 to Office 365 and public folder migration from 2010 to 2013 or 2016.
How much Public Folder Data does your Organization have to Migrate?
Depending on the amount of data and number of Public Folders your organization has, you may want to use a third-party migration tool to facilitate your Public Folder Migration.
With the introduction of Exchange 2013, Microsoft eliminated the Public Folder structure of old. This older Public Folder design within Exchange had problems: mainly scalability, portability and high availability. Microsoft took care of these problems with Exchange 2013 by transitioning to Public Folder Mailboxes. They are very much like Shared Mailboxes, but instead they handle Public Folders.
Because the Public Folders are inside a mailbox that means that they can be members of DAGs (database availability groups) and contained within the existing database infrastructure that you have designed.

Public Folder Limits in Exchange and Office 365
Avoid a migration fail! What to look for in your Public Folders
If you are migrating many Public Folders with large amounts of data, you could hit the 1000-line-item-limit for the creation command. During the process of creating a Public Folder to Mailbox Map process, a CSV file is created based on the maximum mailbox size parameter you set. If that CSV has more than 1000 lines, an error can occur and must be bypassed manually. After the Mailbox map CSV is created, all new top level Public Folders cannot be created until after the migration because it is not contained within the map file. This has caused major business impacts for some clients in the past.

Large amount of folders or data in your Public Folder hierarchy?
These are just some of the limits and challenges with Public Folder migrations but they are the ones that come up most frequently.
The Simple, 4-Step Solution We Recommend
LiquidData offers the first solution that completely de-risks a Public Folder migration to Office 365 or newer versions of Exchange in an easy to use 4-step process. And, you stay within the application from start to finish, never having to leave and get information or run scripts. Let’s go through the four steps in brief:
1. Crawl and Analyze Your Public Folder Hierarchy
2. Partition and Sizing Public Folders
3. Mailbox Creation in the Destination
4. Finalize and Cut Over to your Destination
Ask LiquidData for a demo to analyze and move your Public Folders seamlessly!

Here are some resources about Microsoft Exchange Public Folder and Office 365 limits:
Exchange 2013:
https://technet.microsoft.com/en-us/library/dn594582(v=exchg.150).aspx
Exchange 2016:
https://technet.microsoft.com/en-us/library/dn594582(v=exchg.160).aspx
Office 365:
https://technet.microsoft.com/en-us/library/exchange-online-limits.aspx