
If you don't check your e-mail for more than six months, our system may delete unread e-mail messages older than that.
In detail:
By the way, when we say "check your e-mail", you don't actually have to read it with your eyeballs. Simply logging in using Webmail, or making a successful POP or IMAP mail connection to our servers, marks all waiting mail as "checked" on our servers for the purposes of this policy and prevents it from being deleted, whether or not you actually read it.
We think this is a reasonable policy that controls the size of abandoned mailboxes while making sure we don't delete a recent message you might want. Most ISPs have a much more restrictive policy — for example, Comcast deletes unread mail more than 45 days old, and AOL deletes unread messages more than 28 days old.