I'm a casual user of exim in my home network.

I have a CyrusImap server which I use to access my mail from wherever I am.

Setup

Incoming mail arrives at my ISP and is popped using fetchmail (which runs on the imap machine). It is then lmtp'ed into the imap server.

Outgoing mail is sent via a smarthost (smtp). In the event of 'local' mail hitting the smarthost, it is then forwarded to exim running on the imap server which also uses lmtp to deliver it.

I intend to allow fetchmail to deliver via smtp to the exim server.

My Alternate Exim Configuration

This uses exim on the imap host to receive the mail and forward it through a unix socket.

Domain List

domainlist local_domains = <your domains here>

Routers

localuser:
  driver = accept
  transport = lmtp_delivery

Transport

lmtp_delivery:
  driver = lmtp
  socket = /var/imap/socket/lmtp
  delivery_date_add
  envelope_to_add
  return_path_add
  user = mail