The L= delivery agent
equate is used to limit the length of text lines in the body of a
mail message. If this equate is omitted and if the delivery agent has
the obsolete F=L delivery agent flag set (F=L), sendmail defaults to
SMTPLINELIM (990) as defined in conf.h (SMTPLINELIM). If the F=L is clear (as
it is in modern configuration files), sendmail
defaults to 0 (which means an unlimited line length). The
F=L is honored for compatibility with older
versions of sendmail that lack this
L= delivery agent equate.
Limiting line length causes overly long lines to be split. When an
output line is split, the text up to the split is first transmitted,
followed by the ! character. After that, the
characters defined by the E= delivery agent equate
are transmitted. A line can be split into two or more pieces. For
example, consider the following text from the body of a mail message:
The maximum line length for SMTP mail is 990 characters.
A delivery agent speaks SMTP when the $u sendmail macro
is omitted from the A= equate.
A delivery agent could limit line length to 20 characters with a
With that limit, the preceding text would be split during
transmission into the following lines:
The maximum line len!
gth for SMTP mail is!
A delivery agent spe!
aks SMTP when the $u!
is omitted from the !
Limiting the line length can be useful for programs that
can't handle long lines, such as a 40-character
braille print-driving program. (But such conversions to shorter lines
are probably best left to the specialty delivery agent.)
If the argument to L= is missing or if it
evaluates to 0 or less, the maximum line limit is internally set to
zero, in which case no limit is enforced.
In using V8 sendmail's
mc configuration, the default for the
esmtp, and smtp8 delivery
agents is 990. The default for the relay delivery
agent is 2040. The default for all other delivery agents is 0. To
change the default at the mc level, copy an
existing delivery agent definition and modify it as outlined in Section 20.3.2.