I had asked,
| >Is there any harm in doing something like the following so that procmail can
| >know whether a message came to it via a .forward pipe as opposed to some
| >other non-interactive means (like a cron job, an aliases file, or whatnot)?
|
| > "| IFS=' ' && exec /path/to/procmail -f- DOTFWD=yes || exit 75 #username"
Stephen van den Berg assured me,
| No harm.
As it turned out, there was. The system here barfs on .forwards that are
too long [in character length], and I'm pretty sure that it expands the
$HOME in my path to procmail before measuring.
Ever since I made that change, some of my mail has been repeating on me,
getting delivered three or four times, even though the verbose mailq lists
every delivery as "Xsucceed".
Grumble grumble grumble.