Having migrated over the years from AOL, to Verizon, then OE Express with MSN, and now Gmail, I've learned the hard way:
There is no guarantee that your emails will be readable in the future. Sure, you can fudge around looking for some tool that will let you read them. Sorry, too much hassle for me.
So now I go through the email list at least every 12 months, look for any that might be important in the future (that's not too many!), and do an individual print-out to a PDF. Now THAT I can save and access.