Date: Thu, 6 Aug 1998 16:51:07 -0700
From: Stuart Lynne <sl@poste.com>

And of course it is possible to do a very interesting solution to 
this [virtual domains] using LDAP. 

Selected portions of my configuration using LDAP:

    # Routers entries
 
    # ensure we don't attempt delivery unless MX points to this host
    lookuphost:
      driver = lookuphost
      self = fail_soft
      transport = smtp           

    # punt to director if MX points to this host
    self:
      driver = lookuphost
      self = local
      transport = smtp                    

    # Director entries
							   
    # lookup virtual users in directory IFF MX matches "virtual..fireplug.net"
    virtual_fireplug_net_aliasfile_ldap:
      condition = "${if match{$self_hostname}{virtual..fireplug.net}{$domain}}"
      driver = aliasfile
      search_type = ldap
      expand
      errors_to = sl@whiskey.poste.com
      queries = "ldap:://wilt.fireplug.net/?mailforwardingaddress?sub?(&(mail=$local_part@$domain)(ou=accounts)):\
	    ldap:://wilt.fireplug.net/?mailforwardingaddress?sub?(&(mail=\\\\2a@$domain)(ou=accounts))"
					   
    # specify vacation processing IFF prefix of address is "vacation-"
    vacation_prefix:
      condition = "${if match{$local_part}{.*%.*}{$domain}}"
      driver = smartuser
      prefix = "vacation-"
      transport = vacation_delivery
      new_address = "${if match{$local_part}{(.*)%.*}{$1}{$domain}}@${if match{$local_part}{.*%(.*)}{$1}{$domain}}"
					  
    # specify delivery to pop mailbox IFF prefix of address is "pop-"
    pop_prefix:
      condition = "${if match{$local_part}{.*%.*}{$domain}}"
      prefix = "pop-"
      driver = smartuser
      transport = pop_delivery
      new_address = "${if match{$local_part}{(.*)%.*}{$1}{$domain}}@${if match{$local_part}{.*%(.*)}{$1}{$domain}}"

    # specify delivery to imap mailbox IFF prefix of address is "imap-"
    imap_prefix:
      condition = "${if match{$local_part}{.*%.*}{$domain}}"
      prefix = "imap-"
      driver = smartuser
      transport = imap_delivery
      new_address = "${if match{$local_part}{(.*)%.*}{$1}{$domain}}@${if match{$local_part}{.*%(.*)}{$1}{$domain}}"
                                           
                                                                                        
    # Transport entries

    # perform delivery to pop mailbox 
    pop_delivery:
      driver = appendfile
      #create_directory
      from_hack
      file = /var/mail/${domain}/${lc:$local_part}
      user = mail
      group = mail                               

    # perform delivery to imap mailbox 
    imap_delivery:
      driver = appendfile
      no_from_hack
      prefix = ""
      suffix = ""
      maildir_format
      create_directory
      directory = "/var/imap/${domain}/${length_2:${lc:$local_part}}/${lc:$local_part}/INBOX"
      user = mail
      group = mail            

    # perform vacation processing
    vacation_delivery:
      driver = autoreply
      file = /etc/exim/vacation-msg.txt
      file_optional
      user = mail
      group = mail
      to = $sender_address
      subject = "Autoreply: Vacation message for ${local_part}@${domain}"
      headers = "Mime-Version: 1.0\nContent-Type: multipart/mixed; boundary=\"m1Stw9KgbdL9/HM9\""
      text = "--m1Stw9KgbdL9/HM9\nContent-Type: text/plain; charset=us-ascii\n\
	Content-Disposition: attachment; filename=\"${local_part}@${domain} vacation message\"\n\
	\n\n${expand:${lookup ldap\
	{ldap://src.fireplug.net/?mailAutoReplyText?sub?(&(mail=${local_part}@${domain})(ou=accounts))}{$value}{}}}\n\
	\n--\n${local_part}@${domain}\n\n"
      log = "/var/mail/${domain}/${local_part}_vlog"
      once = "/var/mail/${domain}/${local_part}_vdb"
									    

To use this we have LDAP entries for each user that look something like:

    bjectclass: top
    objectclass: account
    objectclass: mailRecipient
    objectclass: fireMessagingUser
    objectclass: person
    objectclass: organizationalPerson
    objectclass: inetorgPerson
    objectclass: fireNewsAccess
    uid: richard@big-cats.com
    mail: richard@big-cats.com
    mailforwardingaddress: richard@poste.com
    mailforwardingaddress: vacation-richard%fireplug.net@popserver.fireplug.net
    mailforwardingaddress: richard%fireplug.net@popserver.fireplug.net
    userpassword: abcedfg
    cn: richard
    sn: richard
    mailautoreplytext: I'm on vacation

The exim ldap lookup simply finds the entry based on the mail attribute
and returns the mailforwardingaddress attribute value.

This can take several forms and is multi-valued. For example:

    richard@poste.com
		deliver somewhere else, in this case to another
		address on another server

    pop-richard%big-cats.com@popserver.fireplug.net
		deliver into pop mailbox in virtual host directory
		for big-cats.com on server popserver.fireplug.net

    vacation-richard%big-cats.com@popserver.fireplug.net
		perform vacation processing for user

This setup has the interesting property that we can setup multiple
mailbox servers with identical configuration files that will all
deliver mail to mailboxes they are told to deliver to or will forward
to the correct server for the mailbox. All of the interesting 
information about where to deliver mail for a user is in the LDAP
server database. 

In other words, not only can a single host act as a server for
multiple virtual domains, but all of the virtual domains can have
mailboxes spread across a number of physical servers.