I mistakenly changed the option on how long to hold mail on the server and lost a huge number of emails. How do I recover them?

I started receiving the same messages three or four times in Windows Mail Live 2012, so I tried setting a smaller number of days to keep the email on the server. I thought all the old emails were safe on my PC. When I started my PC the next time, Windows Live Mail started deleting all emails that were older than 14 days!. I couldn't stop it other than by shutting down my PC. I keep important emails forever. I have now lost some emails that were very important to me and my family. How can I get them back?