1. Returning E-mailWhen you send an e-mail message to another person, the mail server processes the message and delivers it to the appropriate user's mailbox. For example, if you send a message to "email@example.com," the mail.com server looks for a user named "mrman" to deliver the message to. If the user does not exist, the mail server may bounce the message back to the sender, saying "Sorry, that user does not exist." These messages often come from "Mail Delivery Subsystem" and have a subject line that reads "Returned mail: see transcript for details."
If you receive a bounced message, you may want to check the e-mail address you sent the message to and make sure it was typed correctly. If the address is correct, it may help to read the body of the bounced message for more details. The transcript may say something like "User quota over limit," which means the recipient has reached his or her e-mail quota and must delete some messages and/or attachments in order to receive new mail. If this is the case, you may want to call the person or use an alternative e-mail address to let the person know he or she has some Inbox maintenance to do.