For those interesting in the solution I used:
I used 3 hosts in total, we'll call them dest, mid and source. dest and mid are on the same LAN.
using an SSH tunnel with compression I made a compressed tunnel between mid and source, in order to conserve bandwidth.
samuel@mephisto:~$ ssh -C -L 7777:source:993 localhost cat -
using this link in combination with imapsync ran on mid I'm successfully migrating in-boxes between the hosts without much trouble.
imapsync --host1 localhost --port 7777 --ssl1 --authmech LOGIN --user1 USERNAME1 --password1 PASSWORD1 --host2 dest --user2 USERNAME2 --password2 PASSWORD2 --authmech2 PLAIN
of course, your syntax may vary!
The only reasons I didnt run imapsync on dest or source were because
(a) I cant run it on dest since its a Microsoft Server, and
(b) if I ran it on source I wouldn't of been able to compress the IMAP session.