1998-12-07-17:42:35 Jari Aalto+list.procmail:
As others have noted, the + is sendmail thingie.
Well ... so are .forward files, support for SMTP, all kinds of other cool
things:-). Sendmail has been the proof-of-concept implementation vehicle for
mail transport innovations since it was born. Happily, many features pioneered
in sendmail have made it into other MTAs, like e.g. qmail and Postfix (nee
VMailer). By default qmail uses "-" rather than "+", but it can be configured
to use different rules; Postfix doesn't come with either enabled, but its
example main.cf has a commented-out line to enable "+"-based support.
-Bennett