Some of you may have noticed that more migrations might be failing due to encountering ‘too many bad items’. Upon closer review, you may notice that the migration report contains entries referencing corrupted items and being unable to translate principals. I wanted to take a few minutes and provide more information to help understand what this means, why these are now occurring, and what can be done about them. Ready to geek out?
During a mailbox migration, there are several stages we go through. We start off with copying the folder hierarchy (including any views associated with those folders), then perform an initial copy of the data (what we call the Initial Sync). Once the initial data copy process is complete, we then copy rules and security descriptors. Reviewing a move report shows entries similar to these.
Read about it on the Exchange blog.