What should I do if my Email transfer gets stuck?

On my work email account on my Macbook Pro, I have limited space, and I therefore decided to move some of my achieved messages from the work's exchange server to my hard drive. I dragged and dropped a couple of folders in the left side panel from the "exchange area" to the "on my Mac" area. The folders contained tens of thousands of emails with a total size of 5-10 GB. The moving process has now been going on for about a month and is slowly ticking up, currently at "moving messages 1 of 1772" (sometimes it switches to 16678 of 16887 or something similar after waking up from sleep mode).

I got tired of waiting and eventually pressed "rebuild" and then "synchronize exchange." It has now been stuck at "1 of 1772" for several hours.