Transferring old outlook mails to your new computer

About Importing and Exporting
You can export your email and mail folders, calendar and appointments, tasks, notes and additional content from Outlook as a .pst file and import everything in one go onto a different computer or into another mail profile. The .pst file can be saved to other media just like any other file, however it can only be opened within Outlook; other programs will not be able to open a .pst file.
IMPORTANT: if the .pst contains any sensitive or confidential information (i.e. in your messages, attachments, etc.), it must be adequately protected as per data storage and encryption related requirements.

http://www.cumc.columbia.edu/it/howto/email/exp.html#merge