configs/config.samples/C037

   1 Date: Wed, 22 Nov 2000 17:51:42 -0500 (EST)
   2 From: Dave C. <djc@microwave.com>
   3
   4 [Syntax converted for Exim 4 by PH, 06-Dec-2001. Unchecked.]
   5
   6 Ok.. Ive come up with something which might be worth including in the
   7 cookbook. Credit where it is due, the idea for this came from Nigel's
   8 C014.
   9
  10 I have a setup to support ETRN for a few small (ok, two) domains.
  11 Currently it just leaves all the mail in the exim spool, and uses the
  12 default exim etrn response to flush it out.
  13
  14 I don't like that - I agree with the opinion expressed on the list that
  15 mail should be delivered somewhere else, and then shoved down an SMTP
  16 session by some other program. Ive searched far and wide for something
  17 suitable to do that shoving, and finally hit upon the only program I
  18 trust to do that, handling errors and rejections correctly - exim
  19 itself.
  20
  21 Nigel's solution for 'situation where a site I MX for has a known
  22 outage', combined with a bit of bash scriptery, seems to form a neat
  23 solution. (An intermittently connected host sort of falls under the
  24 'known outage' category ;)
  25
  26 Without any further fluff, here are the details. Additional comments
  27 appear below..
  28
  29 Either the real (intermittently connected) destination host needs to be
  30 listed as the lowest MX (with the exim server as a less preferred) , or
  31 the exim server needs to be the lowest MX, but have a router before the
  32 lookuphost router which uses route_list or something appropriate to
  33 normally deliver mail to the dialup host. The former is probably better
  34 for a host which is usually connected and is only occasionally
  35 disconnected (since other hosts would be able to delivery directly most
  36 of the time, skipping an extra relay), while the latter would probably
  37 work better for the converse ;) This paragraph actually applies anytime
  38 you are using ETRN..
  39
  40 In either case, the routers below must precede whatever router handles
  41 the normal direct-to-dialup-destination..
  42
  43 --
  44
  45 smtp_etrn_command = /etc/exim/etrn_script $domain
  46
  47 [- Content of /etc/exim/etrn_script: -]
  48 #!/bin/sh
  49
  50 # Where exim lives
  51 EXIM=/usr/sbin/exim
  52
  53 # Something appropriate to generate a temporary unique string
  54 UNIQ=`head -c100 /dev/urandom | md5sum | cut -f 1 -d" "`
  55
  56 arg=$1
  57 domain=`echo $arg | sed 's/^\#//g'`
  58
  59 if ( test -f /var/spool/etrn/${domain} ); then
  60  exim_lock -q /var/spool/etrn/${domain} "mv /var/spool/etrn/${domain} /tmp/etrn-bsmtp-${UNIQ}"
  61  ( cat /tmp/etrn-bsmtp-${UNIQ}
  62    echo "QUIT" ) | $EXIM -bS -oMr etrn_requeue
  63  rm -f /tmp/etrn-bsmtp-${UNIQ}
  64 fi
  65
  66 $EXIM -R $domain
  67
  68 [- end of etrn_script -]
  69
  70 [- exim transport -]
  71
  72 bsmtp_for_etrn:
  73  driver=appendfile
  74  file=/var/spool/etrn/$domain
  75  user=exim
  76  batch_max = 1000
  77  use_bsmtp
  78
  79 [- routers -]
  80 [- You probably would want to put the domains in a file or a dbm and
  81 [- adjused the 'domains' setting appropriately for both of these..
  82
  83 # If any message has already been delivered to the bsmtp file,
  84 # this will detect the existence of the file and all messages will
  85 # go there, regardless of age.
  86 etrn_already:
  87  driver = accept
  88  transport = bsmtp_for_etrn
  89  require_files = /var/spool/etrn/$domain
  90  domains = etrntest.somedomain.com
  91
  92 # If a message has been on the queue for over the specified amount of
  93 # time, this will catch it and drop it into the bsmtp file
  94 etrn_delay:
  95  driver = accept
  96  transport = bsmtp_for_etrn
  97  condition = ${if >{$message_age}{1800} {yes}{no}}
  98  domains = etrntest.somedomain.com
  99
 100 [- -]
 101
 102 Basically, this setup lets exim try to deliver to the real host for up
 103 to whatever time is specified in the \%etrn_delay%\ router. (1800 seconds =
 104 30 minutes), and then delivers all waiting messages, and any further
 105 messages, directly to a BSMTP file. This setup uses one big BSMTP
 106 file per domain, it probably wouldnt be too complex to have it use separate
 107 files.
 108
 109 When the \^etrn_script^\ runs, it locks and renames the BSMTP file, and
 110 reinjects the messages to Exim, which (presumably) will now be able to
 111 deliver them. If it can't, then once they are too old they will again
 112 be sent off to the BSMTP file.. (If for som reason this occurs over and
 113 over without Exim being able to deliver them, eventually the messages
 114 will be returned with \*too many Received headers*\; this is a good
 115 thing, since their age will never get high enough for them to be
 116 returned by any retry rules).