The Powerhouse Museum in Sydney has lots of paper/stone/other correspondence from over the centuries, and is now embarking on an archive of email. If you're in Australia and would like to submit emails, here's the site with more info:
1.Life and Laughter— funny forwards and tales of hilarity from everyday life
2.Touching tales— personal e-mails that touch the soul
3.Family— the first steps to the last, and all things in between
4.Love and romance— e-mails to make you go 'oooh'
5.E-mails you regret sending— e-mails that make you go 'arrrgghh'
6.Embarrassing typos— it's amazing how easily meaning goes ashtray with a small typo
7.Current affairs— news and its effect on us, whether it's local or from overseas
8.Complaints— for those moments when only 'putting it in writing' will do