Sendmail, 3rd Edition

Parts of a Queued Message

When a message is stored in the queue, it is split into pieces. Each piece is stored as a separate file in the queue directory. That is, the header and other information about the message are stored in one file, while the body (the data) is stored in another. All told, six different types of files can appear in the queue directory. The type of each is denoted by the first two letters of the filenames. Each filename begins with a single letter followed by an f character. The complete list is shown in Table 11-1.

Table 11-1. Queue file types

File	§	Description
df	Section 11.2.2	Data (message body)
lf	Section 11.2.3	Lock file (obsolete and removed as of V5.62)
nf	Section 11.2.4	ID creation file (obsolete and removed as of V5.62)
tf	Section 11.2.6	Temporary qf rewrite image
xf	Section 11.2.7	Transcript file
qf	Section 11.2.5	Queue control file (and headers)

The complete form for each filename is:

Xfident

The X is one of the leading letters shown in Table 11-1. The f is the constant letter f. The ident is a unique queue identifier associated with each mail message.

In the following sections we first describe the identifier that is common to all the queue file parts, then describe each file type in alphabetical order. The internal details of the qf file can vary depending on the version of sendmail, so it is discussed separately at the end of this chapter.

The Queue Identifier

To ensure that new filenames are not the same as the names of files ...