When Postfix makes local deliveries it transfers the contents of messages to the local message store. The most common types of message stores are the traditional mbox format and the newer maildir style. Both use regular files to store messages, but they are structured in different ways. In Postfix, you specify maildir style by including a trailing slash when you configure any mail file or directory parameters (see configuration information later in this chapter).
Historically, Unix systems have used a single file to
store each user's email messages. This type of message store format is
commonly referred to as mbox. Each message
within the file starts with a line that begins with the word
From. It is important that the string start
on the first character of the line, and that there is a space after
the end of the word. The From line is commonly referred to as
From_ with an underscore character to
indicate the space following the word. Don't confuse the
From_ line used for separating messages
within an mbox file with the
line included in email message headers. The last line of a message is
always a blank line.
From_ line looks
like the following:
From firstname.lastname@example.org Sun Feb 3 16:54:01 2002
As described, the line starts with the word
From followed by a space. Following the space is an email address that is usually the envelope address of the message. Following the envelope address is the date of delivery in the common Unix date ...