running fetchmail with
poll pophost localdomains domain1 domain2 domain3 with proto POP3
user 'login' there with password 'password' is * here
and qmail on the local mailserver. When two local accounts receive the
same message, one in To:, one in Cc:, they both get it twice. Does this
sound familiar to someone?
You *MUST* properly configure the "envelope" option and if the upstream
uses qmail and your domain as virtual domain, also "qvirtual".
If the upstream doesn't provide a reliable envelope (look for
X-Original-To, X-Envelope-To, Envelope-To, Delivered-To in the mail
headers), then you're lost and need to stop using multidrop or you need
to ask your ISP to provide for such headers, or if they fail to provide
for that, switch ISP to someone who does.
Any To: or Cc: parsing is inherently unreliable and will fail. What
you're seeing is a less severe failure variant, the more severe will be
misfiled or lost mail when you're listed in Bcc: - because that won't
arrive at your site.