Is there a Linux mail server with an outgoing pickup directory?

On my Exchange server I can drop appropriately formatted text files in the "pickup" directory and Exchange will process them.

I'd like to split this bulk mailing functionality onto another box to protect our business mail IP from the bumpy ride that our monthly newsletter gives us.

I should note at this point that the mailing is opt-in with an opt out link included and only goes to people who pay to be a member of our organisation

The ideal solution for me would be to add a linux box to use just for this purpose so we're not paying for Exchange licenses.

So is there a linux equivalent of the Exchange pickup directory?

From serverfault Paul D'Ambra

• You could toss something together quickly using incron and sendmail.

  Chris S : +1, just about every MTA could use cron + `sendmail` (or equivelent) to accomplish this.

  Paul D'Ambra : The time it would take us to shift our implementation to this means we can't really justify it (we don't have inhouse Linux experience that covers it) but this does seem to be the best answer. Cheers!
  From Ignacio Vazquez-Abrams

• There are many mailing list management tools that will happily work with most mail servers, like Sympa or Mailman.

  From wazoox

• Postfix's maildrop queue directory works like this by default; see the following for details of how Postfix processes mail delivery: http://www.postfix.org/QSHAPE_README.html#maildrop_queue

  However, the formatting expected is a little odd, so it's much easier just to use the sendmail wrapper to deliver mail by redirecting to stdin like so: sendmail -i -t < your.msg.

  Just make sure your message is properly formatted with the correct headers.

  From gravyface