Outlook Email Backup

Launch Outlook 

If this prompt pops up > click Use Old Data

Backup Email

File > Import  

Export to a file >Outlook Data File (.pst) > 

Select email account for all folders > Save it in C:\Outlook Backup\backup.pst > Finish

It will export all of the old emails into a .pst file in that location. It will take some time depending on how big the inbox is and how fast the computer is.