2.1. A Metaphorical View

To describe in everyday terms what Sendmail does, we must define some mail terms. It might help if you can remember back to your youth when you first learned to write a business letter. This is going to seem basic, but please indulge us.

A business letter that you send through the postal system has some standard parts to it. On the envelope there is a place for recipient (or addressee) information and a place for sender information. On the letter itself there is also sender and recipient information, though perhaps with less detail. The date is included. Following those items are the greeting, body, closing, and signature. In a proper business letter, all these parts should be present. If it is a memorandum, things are in a different order, but the same information should still be there.

The envelope may contain different information than the addresses inside the letter. You must have received such mail. The envelope has your name and address on it, but in the letter (or memo) the address indicates a mailing list ("To: Technical Staff," for example, or "Dear Parent").