F=U
Use UUCP-style From line All versions
The F=U delivery
agent flag causes sendmail to
prefix a five-character "From" line to the start of the headers
if there is not already one there. Whether one was
prefixed or not, this delivery agent flag also tells
sendmail to add the words
remote from
host to the end of that line,
and also requires that $g be in the form
host!....
The F=U delivery
agent flag is required when a neighbor UUCP site
runs an old (or possibly SysV) version of the
rmail program. The newer BSD
versions of rmail do not
require this delivery agent flag.
Note that the F=n
flag (F=n on page 776), if
specified, overrides this F=U flag.
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