Black has identified three types of email users. Type A users delete everything fairly quickly and never hit their mailbox-size ceiling, so administrators generally don't need to worry much about them. The two other types store messages for future use, either because the messages contain some business value (Type B) or because they answer a question that will probably come up again (Type C). Type B users are fairly organized—they use some kind of folder structure to make it easy to locate items, filing messages by project name, for example. Their mailboxes might grow steadily, but they seldom contain nonbusiness mail. Type C users are disorganized. Their Inboxes may have 1000 or more items, including daily newsletters from a year or two ago, and their mailboxes grow rapidly. Fortunately, says Black, Type C users appear to comprise only about 10 percent of the population.
First there are those that file their messages carefully (magpies). Just over 90% of those questioned use more than 10 separate files. Just under half feel so overwhelmed by information that they ignore new messages (ostriches). And over half of those surveyed amass a huge amount of email, refusing to get rid of old messages just in case they might need them (squirrels). In fact, 8% could point to over 2,000 emails in their inboxes.