Is your email cloud-based, using a service such as Outlook.com or Yahoo or Gmail? If so, do you ever think about taking a backup of all your archived messages so that you have a searchable copy in case you have problems with your online account?
Mailstore Home makes this really easy, and it works with all the leading email providers. Just tell it your account details and it'll fetch copies of all your online messages into its own searchable database. By default, it never deletes copies from your remote mailbox, so it's safe to use. Although you can change this setting if you want, and have it delete your online copies once they have been archived to your PC.
The program even works in 2 directions. If you need to, you can restore messages from your offline backup, right back into your mailbox.