With the advent of search, users are no longer required to physically organize email content around folders. It also means that search-savvy users can end up with folders containing over 50,000 items. MigrationWiz always uses paging and batching to migrate mailbox content as quickly as possible. In spite of all this, we cannot migrate faster than what the source system can handle. And it turns out that the Exchange Web DAV API can perform very poorly when retrieving content from very large folders:
- The Exchange team publishes useful information about mailbox size limits: their recommendation is no more than 2500-5000 messages per folder.
- The TechNet website has useful information about the performance impact of high item counts and restricted views on client and backup performance.
The good news is that, in most cases, we have the ability to switch your migration to use other protocols such as Exchange Web Services or IMAP. Using those protocols, we can speed up your migration by a factor is 3 to 10. So if you are migrating Exchange mailboxes containing very large folders and performance is not as fast as you’d expect, we do have some options for you. Contact our support team using our 24/7 included email support and we’ll get the ball rolling.