In <85766$484c5363$d5e52b02$4323@news.inode.at>, on Sun, 08 Jun 2008
23:47:15 +0200, Alexander Joelly, alex@joelly.net wrote:

> is it possible on sendmail to duplicate all incoming mails and forward
> it to two different additional mail-servers?

Yes.

If you read the doc for sendmail,
$ locate sendmail/cf/README
it mentions using virtusertable, though that seems to
be a secondary recommendation after procmail. It
even gives an example procmail rule to do... not exactly
the same thing, but similar:

a common question is "how do I forward all mail for a given
domain to a single person?". If you have this mailer
defined, you could set up a mailertable reading:

host.com procmail:/etc/procmailrcs/host.com

with the file /etc/procmailrcs/host.com reading:

:0 # forward mail for host.com
! -oi -f $1 person@other.host

A quick perusal through the procmail docs should
have you creating duplicate e-mails in no time.

$ man procmail
$ man procmailex
$ man procmailrc