When you do a migration and the Exchange setup fails, there's a trick to reading the log file.
Open up the Exchange setup log file and scroll ALLLLLL the way to the bottom.
Now look for a place in the log file where the items indent --
I've highlighted the indentation area you should look for as the clue of where the barfage occured.
Right above that indentation is where you should look for hints for errors. Look for some key phrases and words and google/bingle the words.
In this case there was an email address policy that was causing the block "on Address List or Email Address Policy "ABC Email Address" is invalid".
But the key is scrolling all the way to the bottom and reading from the bottom up.