Transfer emails from old machine with 10.6.8 to new iMac running Yosemite

I have an older MBP running 10.6.8 (Snow Leopard), on which the OS cannot be upgraded any further.

I have recently purchased a new iMac, which is running Yosemite.

How do I transfer all my emails, including folders and contents to the new machine?

The two machines can see each other on the network, but cannot seem to access each others files.

If anyone can help I would be most appreciative, but please note that I am a novice, so I do need step by step instructions.

Thanking you all in advance.

George