Transfer Mail inbox from one mac to another mac's Mail inbox?

In Mail on the old MB, go to Mailbox > Archive Mailbox. That should put everything into one convenient place that you just copy over to the MBP. From there, you should be able to go to File > Import Mailbox, then Select "Mail for OSX" and just select the .inbox file that was created. That should work right, though I have never done it for sure myself. This is one of those things where the help files and a quick google search may do better than relying on us to give you an answer...

 

The file would be called inbox.mbox

Just archive the old inbox onto the desktop then copy it over to the new mac.


Then import the *.mbox folder

It will look like this :

 

Time Machine is the simplest way to go, otherwise...

a. IMAP/Exchange mailserver: your files stay on the server, changes from the client are made on the server. Your MBP would get all the messages off the server as they were on your other machine. Gmail offers free IMAP.

b. POP mailserver: normally the default is to download the messages (remove from server as downloaded).

c. there must be lots of other ways, like copying over the local mail files, but my laziness prevents me from understanding its ins and outs.

In case of b., with OS X Mail drag mail from POP accounts over to an IMAP account (solution a). But if you can't deal with that, go for door c.

 

I'm not sure that Time Machine actually fully backs up the Mailboxes. I seem to recall loosing A BUNCH of mail when I tried doing a clean install of Leopard (instead of the previous Tiger->Leopard I had) and restoring from Time Machine.
I would for sure archive the mailboxes in the way described just to be safe...