The lines of text that form the message header are saved to the qf file, one per H line. Any header lines added by sendmail are also saved to H lines in the qf file.

The form of the H line is:

Hdefinition

The H must begin the line, and the definition must immediately follow with no intervening space. The definition is exactly the same as, and obeys the same rules as, the H commands in the configuration file (Section 25.1). Beginning with V8.10, if the header lacks header flags, an empty pair of ? characters are prefixed to the definition.

When sendmail writes header lines to the qf file, it preexpands sendmail macros (replaces expressions such as $x with their values) and preresolves conditionals ($?, $!, and $.). Beginning with V8.10, the headers in the qf file might have been rewritten by rule sets.

The order in which H lines appear in the qf file is exactly the same as the order in which they appear in the delivered message.