Previous Next Table of Contents

6. Glossary


An alias is a way of forwarding an e-mail address to one or more new destinations.


Star-like symbol, ASCII code 42 decimal. Usually rendered six-pointed, but has also been spotted with five or eight points.


Returned, undeliverable mail. Also the act of returning undeliverable mail. Bounces are returned to the sender address in the envelope* of the mail; the sender given in the header* is not used.


Dynamic|Distributed Name Server|System. A mechanism on internet to find addresses and other things associated with host names.


Information about a mail message that is not in the header. This information is used by MTAs* to determine where mail must go, and if not deliverable, where it is to be returned. This information is typically transferred with commands of the SMTP* protocol.


Extended SMTP*. Has some more features.


The initial part of a mail message, containing more or less meta information about the message; who sent it, what it is about, what it looks like, to whom you are to answer, etc. The structure and meaning is described in RFC* 822.


A destination where mails are sent to. It is more general than your in-box that contains the mails delivered to you. A mailbox can also be a program (which prints the mail to a printer) or other things.

Mail domain

The part after the @ of an email address. This is often called the "fully qualified host name", but with more modern mail transport (MX records), it's not really a host any more. So I prefer the term "domain".


A "channel" for sendmail via which to output mails. This is a very general concept, including talking SMTP* or UUCP* to other mail servers, delivering a mail to a mailbox, piping a mail to a program; anything via which a mail can be sent ending up of sendmail's control.


Translate an address. This is the pure act of translation; it does not necessarily mean that the mail gets sent to another place. For redirecting e-mails there is aliasing*.


Mail Transfer Agent. A program that transfers mail from one place to another. Sendmail is an MTA.


Mail User Agent. A program that manages mail messages (on behalf of a user). Eudora, elm, pine, etc. are examples of MUAs.

Return Address

Place where to send the bounce* when an email turns out undeliverable. The return address is in the envelope* of the email. Some people know this as the "From " header*, since it often saved in mailboxes looking like a header line. It really isn't; it's part of the envelope.


Request For Comments. Documents written as proposal for a standard on the internet. They do not always make it to standard, but the ones about SMTP* (RFC 821) and mail message structure (RFC 822) did.


Simple Mail Transfer Protocol. A commonly used protocol (language) used by MTAs* to exchange mail. Described in RFC* 821.


Unix to Unix CoPy. A protocol used on many unix systems to transfer files between them. E-mail can also be transferred with this system.

Previous Next Table of Contents