Email is messy. It adheres to standards when it’s being sent down the wire, but there’s no consistency about how it’s stored. This makes it easy to lose. Politicians are especially hard-hit by this problem, and often inadvertently lose all their email, especially when they leave office.
There are several problems with preserving email. The first is that it may not even be on a computer that you control. There are three major ways to get email: (1) POP3, a protocol which delivers all mail to your computer; (2) IMAP, where the mail is kept on the server and delivered to you as needed; and (3) webmail, where messages aren’t delivered to you as such, but are available for reading on your browser. Only in the first case can you directly export and back up all your mail. On the other hand, cases (2) and (3) store the mail on a server, where hopefully it’s backed up professionally.
Let’s look at these one at a time. POP3 (short for Post Office Protocol version 3), which is defined by IETF RFC 1939, defines a particular way of getting mail to your computer, but it says nothing about its format. RFC 822 defines the format of the message as a series of headers (e.g., “To:” and “From:”) followed by a body, but it says nothing about the format of the body except that it’s ASCII text. Yes, that’s right; all the JPEG images, applications, and Unicode Japanese text that you get in your email have to be sent as ASCII. How is this done? With yet another standard, Multipurpose Internet Mail Extensions or MIME. It takes six RFC standards to specify this.
Then with POP3, the MIME-encoded mail with RFC 822 headers arrives on your computer for storage. So there must be yet another standard for this, right? Well … not really. Each email client has its own way of storing your messages. This can be a problem. If you switch from one client application to another, you may not be able to read your old mail any more. Fortunately, many mail clients use MBOX natively (e.g., Thunderbird) or are able to export mail to MBOX format. There’s an IETF standard for this, too; RFC 4155. Unfortunately, it’s more of an attempt to codify the existing chaos than to lay down a standard. It defines a “default” (their quotation marks) MBOX format, and today most client applications support it. It’s possible, though, that you’ll encounter MBOX files which some applications can’t import properly.
With IMAP (Internet Message Access Protocol), the situation is about the same except that your mail may not all be on your computer. You may have to take the extra step of downloading all your messages before you can export them, or exporting may just be very slow as all the messages have to be received. If you don’t keep up to date on this and you lose your account (for example, because a spammer hijacks it and your provider has to shut it down), you lose any unsaved mail.
With webmail, you’ve got the same risks and some others. Read this story of how author James Fallows’ wife experienced having her GMail account hijacked by a spammer, and nearly lost all the mail in the account. Exporting from a webmail account can be difficult unless your service provides a way to do it. Some do; for instance, GMail provides an option for getting all your mail by IMAP or POP.
If your mail is on your computer, you still might not know exactly where it is. Typically it’s buried in some directory you didn’t create. It’s different for each application, and you should find out for the application that you’re using, so you can make sure it’s being backed up.
Outlook, as you might expect, has its own issues. It has an export function but exports into a proprietary format. Fortunately, there are tools for converting this to MBOX format. One clever trick is to use Thunderbird, enhanced by Import-Export Tools, to “export” mail to MBOX format by importing it, even if you don’t otherwise use Thunderbird.
Another reason preserving email is messy is that it’s often 90% or more junk: notes of no lasting importance, spam, and things that could get you into a courtroom or out of your job. A short message might have a huge attachment that you don’t notice and don’t need. Saving all your email can take up an inconvenient amount of space after a while. If you have a good filtering system that organizes your messages into mailboxes, you can decide which boxes are worth saving and which should be thrown away.
Suggestions: With your own mail, make sure you have a copy of your important messages on your own computer and that they’re being backed up. If you’re responsible for site backups, make sure that people’s mail is getting backed up. If policy dictates that people’s mail should be saved then they leave, make sure that when their accounts are closed, their mail is saved in an application-neutral format such as MBOX, and that unauthorized people can’t get at it till it’s been checked for confidential information.