We researchers and writers are necessarily hoarders. We wind up with hundreds of reference volumes and file cabinets full of old manuscripts and back issues of long-forgotten publications. If we give it much thought at all, we assume that our heirs will donate (possibly sell) the material to a deserving archive or library—or at least allow interested people to cherry-pick what’s most useful to them.
But what about emails?
I've been cataloging aviation, naval, and generic history emails since the late 90s, knowing that I'm unlikely to look at many/most of them again but they might be available for whomever winds up with access to my computer(s). It's a subject I've raised once or twice with other practitioners. Our emails contain an enormous amount of info that likely has never been published—and may never appear in print. But my computer files already contain irreplaceable first-hand accounts of historic events, often sent by participants now long deceased. So do the computers of nearly every colleague I know.
When I say I'm cataloging emails, mainly that means I'm retitling them for greater relevance. You know the internet: Who Killed The Red Baron can morph into alligator wrestling with astonishing speed. So I try to consolidate specific subjects into a single email rather than have multi messages with relevant passages in each. I don't always get it done but hey, I'm trying to make a living here...
Meanwhile, what to do?
Suggestion: leave written instructions granting permission for specific people to access your email account, updated with current passwords. (Yes, we know about the Good Buddy's Last Request to purge your computer files before next of kin start looking at them!) At some point your email account will go flatline, or become inaccessible. So it’s critical to make arrangements for preserving your messages before the account is cancelled.
Maybe an option is to copy groups of emails to external storage: CDs or thumb drives, thus avoiding the problem of accessing a decedent's email account. But remember: BACKUP, BACKUP, BACKUP. One of my oft-used thumb drives recently died, taking a couple of books and many articles with it. Fortunately I believe in BACKUP, BACKUP, BACKUP. The Time Machine external drive linked to my iMac has an enormous amount of storage—I may never fill it up solely with text.
Besides emails, I keep text files of my articles, arranged by general subject. At some point those also would be helpful to later researchers, with the added benefit of being searchable. That leaves the door open to plagiarism but if it's posthumous, that seems less a concern though presumably anyone's heirs would be entitled to compensation. Just another aspect of the brave new cyberworld.
Thinking downstream: one aspect that might pose problems is that inevitably emails focusing on one subject often contain, um, controversial, nay, scandalous comments, some irrelevant to the immediate topic. I doubt that many folks would scrub hundreds of egrams to delete such things before releasing the material to “the cloud,” or whatever. Of course, there should be no legal or other concerns if released posthumously but by then the procedure for retaining and disseminating the material could pose greater (practical) problems.
Finally, I'll note that I maintain a master file that lists all my published articles, some 650 so far, dating from 1965. That’s important since I wrote my first six books and about 100 articles on a Royal Standard that was older than I was. The list makes it possible to find pre-computer texts both for reference and for transcribing if an article is to be reprinted. My personal best is three reprints of one article, and if I hadn't kept those long-ago magazines it would not have been possible. Later researchers could benefit from that kind of info. (My bride took some convincing on that score, but eventually she accepted the rationale. She did not accept the rationale that for a bachelor author, floor space = shelf space.)
Remember: for a researcher there’s no such thing as too much information. But there is such a thing as too little. Your email files could go a long way in helping preserve history far into the 21st century.