Migration assistant lost files and emails

HI,

I used Migration assistant to move files from an old imac to a new macbook air today. When the process was done I discovered that all of the emails on my new computer that are older than today are gone and my documents folder is empty.

I'm sure I did something wrong, though all I did was follow the apple tutorial and the computer prompts.

Is there anyway to recover my files ?

Thanks for any help.