openldap/clients/mail500

*** WARNING:  Preliminary ***

This is the README file for mail500, a mailer that does X.500 lookups
via LDAP.

If you are planning to run mail500 at your site, you need to create a
configuration file.  Previous versions required modifying the source
code for configuration.  This is no longer necessary.
there are several

*** WHAT mail500 DOES: ***

mail500 is designed to be invoked as a mailer (e.g., from sendmail),
similar to the way /bin/mail works.  It takes a few required arguments
and then a list of addresses to deliver to.  It expects to find the
message to deliver on its standard input.  It looks up the addresses in
X.500 to figure out where to route the mail, and then execs sendmail to
do the actual delivery.  It supports simple aliases, groups, and
mailing lists, the details of which are given below.

*** HOW IT WORKS (from the sendmail side): ***

The idea is that you might have a rule like this in your sendmail.cf
file somewhere in rule set 0:

R$*<@umich.edu>$*	$#mail500$@umich.edu$:<$1>

This rule says that any address that ends in @umich.edu will cause
the mail500 mailer to be called to deliver the mail.  You probably
also want to do something to prevent addresses like terminator!tim@umich.edu
or tim%terminator.rs.itd.umich.edu@umich.edu from being passed to mail500.
At U-M, we do this by adding rules like this to rule set 9 where we
strip off our local names:

R<@umich.edu>$*:$*                 $>10<@>$1:$2
R$+%$+<@umich.edu>                 $>10$1%$2<@>
R$+!$+<@umich.edu>                 $>10$1!$2<@>

You can also feed complete FQDN addresses to mail500.  For instance,
you could define a class containing the list of domains you want to
serve like this:

FQ/etc/mail/mail500domains

and then use a rule in rule set 0 like this:

R$*<$=Q>$*		$#mail500 $@$2 $:<$1@$2>

See the sample sendmail.cf in this directory for more details.
For sendmail 8.9 (and later) users can use MAILER(mail500) if
mail500.m4 is placed within sendmail's cf/mailer directory.

The mail500 mailer should be defined similar to this in the
sendmail.cf file:

Mmail500, P=/usr/local/etc/mail500, F=DFMSmnXuh, A=mail500 -f $f -h $h -m $n@$w $u

This defines how mail500 will be treated by sendmail and what
arguments it will have when it's called.  The various flags specified
by the F=... parameter are explained in your local sendmail book (with
any luck).  The arguments to mail500 are as follows:

	-f	Who the mail is from.  This will be used as the address
		to which any errors should be sent (unless the address
		specifies a mailing list - see below).  Normally, sendmail
		defines the $f macro to be the sender.

	-h	The domain for which the mail is destined.  This is passed
		in to mail500 via the $h macro, which is set by the
		$@ metasymbol in the rule added to rule set 0 above.
		It's normally used when searching for groups.

	-m	The mailer-daemon address.  If errors have to be sent,
		this is the address they will come from.  $n is normally
		set to mailer-daemon and $w is normally the local host
		name.

The final argument $u is used to stand for the addresses to which to
deliver the mail.

*** HOW IT WORKS (from the mail500 side): ***

When mail500 gets invoked with one or more names to which to deliver
mail, it searches for each name in X.500.  Where it searches, and what
kind(s) of search(es) is controlled by a configuration file.  There
are a number of different approaches to handling mail and no general
rules can be given.  We will however present some examples of what you
can do.  The new mail500 is designed to be flexible and able to
accommodate most scenarios.

For instance, if you are following the mail distribution model that
the old mail500 used, you need lines in the configuration file like
these:

search  ldap:///ou=People, dc=OpenLDAP, dc=org??sub?\
	(|(uid=%25l)(cn==%25l))

search  ldap:///ou=System Groups, ou=Groups, dc=OpenLDAP, dc=org??sub?\
	(&(cn=%25l)(associatedDomain==%25h))

search  ldap:///ou=User Groups, ou=Groups, dc=OpenLDAP, dc=org??sub?\
	(&(cn=%25l)(associatedDomain==%25h))

As you can see, searches are described by using LDAP URLs.  You can
have as many searches as you want, but the first search that succeeds
completes the processing for a recipient address.  You can provide an
attribute list in the URL and it will be honored.  Otherwise, the
attribute list will default as explained below.

Filters can contain substitutions.  Actually, they *should* contain
substitutions or the search result would not change with the recipient
address.  Since the usual substitution character is % and it has
special meaning in URLs, you have to represent it according to the URL
syntax, that is, %25, 25 being the hex code of %.  The filter can be
as complex as you want and you may make as many substitutions as you
want.  Known substitutions at this time are:

        %m   The recipient address we are considering now, maybe fully
	     qualified
	%h   The host, that is, the value of the -h argument to
	     mail500
	%l   The local part from %m
	%d   The domain part from %m

So, in the above example, if the recipient address were
name@OpenLDAP.org, mail500 would do the the following searches,
stopping if it found anything at any step:

	Search (18) [2]: dc=org@dc=OpenLDAP@ou=People
	Search subtree (uid=name)
	Search (18) [3]: dc=org@dc=OpenLDAP@ou=People
	Search subtree (cn=name)

	Search (18) [4]: dc=org@dc=OpenLDAP@ou=Groups@ou=System Groups
	Search subtree & ((cn=name)(associatedDomain=OpenLDAP.org))

	Search (18) [5]: dc=org@dc=OpenLDAP@ou=Groups@ou=User Groups
	Search subtree & ((cn=name)(associatedDomain=OpenLDAP.org))

[Beware: Currently unimplemented]
You can also specify whether you want search results that matched
because the entry's RDN matched the search to be given preference
or not.  At U-M, we only give such preference in the mail group
portion of the searches.  Beware with this option:  the algorithm
used to decide whether an entry's RDN matched the search is very
simple-minded, and may not always be correct.

*** HOW IT WORKS (from the X.500 side): ***

First you need to decide what attributes you will search for and what
attributes will be used to deliver the message.  In the classical
mail500, we would search by uid or cn and deliver to the mail
attribute.  Another model is to search by the mail attribute and
deliver to something else, such as the uid if determined that the user
has a local account.

*** THE CONFIGURATION FILE

The configuration file is composed of lines that prescribe the
operation of mail500.  Blank lines are ignored and lines beginning
with # are considered comments and ignored.  Outside comments, the
sequence '\', newline, whitespace is ignored so that long lines can be
split for readability.

Attribute Definitions

Lines starting with 'attribute' define the semantics of an attribute.
Notice that attributes will be considered in the order they are
defined in the configuration file.  This means that the presence of
some can preempt processing of other attributes and that attributes
that simply collect needed information must be defined before others
that use that information.  The format is:

attribute name [multivalued] [final] [multiple-entries] [<syntax>] [<kind>]

If the attribute is "multivalued", all values will be considered.  If
it is not and several values are found the entry is declared in error.

If the attribute is "final", its presence in an entry prevents further
analysis of the entry.

If the attribute is "multiple-entries" and it is of an appropriate
syntax that can point to other entries, all such entries are
considered, otherwise the entry is in error.

The known kinds are:

recipient		The value(s) of this attribute should be
			used as the address(es) to deliver the message
			to if they are in an appropriate syntax.  If
			they otherwise point at other entries, they
			should be retrieved and expanded as necessary
			to complete the resolution of this entry.  The
			process is recursive and all.

errors			The value(s) of this attribute represent the
			entities that should receive error messages
			for mail messages directed to this entry.
			The presence of an attribute of this kind
			force a change in the envelope sender address
			of the message.

The known syntaxes are:

local-native-mailbox	An unqualified mailbox name
rfc822			A fully qualified RFC822 mail address
rfc822-extended		Currently identical to rfc822
dn			The Distinguished Name of some other entry
url			A URL either of the mailto: or ldap: styles,
			others styles, notably file:, could be added.
			No substitutions are supported currently.
search-with-filter=<filter>	Do a search on all known search bases
			with the give filter.  The only currenty
			substitution available is %D, the DN of the
			current entry.

The default attributes to search

A line starting with "default-attributes" contains a comma-separated
list of attributes to use in searches everytime a specific list is not
known.

Search bases

As shown in the example above, lines starting with "search" provide
the search bases to use to initially try to resolve each entry or when
using attributes of syntax "search-with-filter".

*** EXAMPLES

A configuration file that approximates the operation of the old
mail500 runs as follows:

attribute errorsTo				errors dn
attribute rfc822ErrorsTo			errors rfc822
attribute requestsTo				request dn
attribute rfc822RequestsTo			request rfc822
attribute owner					owner dn
attribute mail			multivalued 	recipient rfc822
attribute member		multivalued	recipient dn
attribute joinable	multiple-entries	recipient \
	  search-with-filter=(memberOfGroup=%D)

default-attributes objectClass,title,postaladdress,telephoneNumber,\
	mail,description,owner,errorsTo,rfc822ErrorsTo,requestsTo,\
	rfc822RequestsTo,joinable,cn,member,moderator,onVacation,uid,\
	suppressNoEmailError

# Objectclasses that, when present, identify an entry as a group
group-classes mailGroup

search  ldap:///ou=People, dc=OpenLDAP, dc=org??sub?\
	(|(uid=%25l)(cn==%25l))

search  ldap:///ou=System Groups, ou=Groups, dc=OpenLDAP, dc=org??sub?\
	(&(cn=%25l)(associatedDomain==%25h))

search  ldap:///ou=User Groups, ou=Groups, dc=OpenLDAP, dc=org??sub?\
	(&(cn=%25l)(associatedDomain==%25h))

A configuration that approximates the semantics of the mailRecipient
and mailGroup classes used by Netscape:

attribute mgrpErrorsTo				errors url
attribute rfc822ErrorsTo			errors rfc822
attribute mailRoutingAddress	final		recipient rfc822
attribute mailHost		final		host forward-to-host
attribute uid			final		recipient local-native-mailbox
attribute uniqueMember		multivalued	recipient dn
attribute mgrpRFC822MailMember	multivalued	recipient rfc822-extended
attribute mgrpDeliverTo		multivalued multiple-entries recipient url

default-attributes objetcClass,mailRoutingAddress,mailHost,uid,uniqueMember,\
	mgrpRFC822MailMember,mgrpErrorsTo,rfc822ErrorsTo

# Objectclasses that, when present, identify an entry as a group
group-classes mailGroup

search  ldap://localhost/dc=OpenLDAP,dc=org?\
	objectClass,mailRoutingAddress,mailHost,uid?\
	sub?\
	(&(|(mail=%25m)(mailAlternateAddress=%25m))(objectClass=mailRecipient))

search  ldap://localhost/dc=OpenLDAP,dc=org?\
	objectClass,uniqueMember,mgrpRFC822MailMember,mgrpErrorsTo,mgrpDeliverTo,rfc822ErrorsTo?\
	sub?\
	(&(|(mail=%25m)(mailAlternateAddress=%25m))(objectClass=mailGroup))

[ The rest is from the original README and I did not rewrite it yet ]

In X.500, there are several new attribute types and one new object
class defined that mail500 makes use of.  At its most basic, for normal
entries mail500 will deliver to the value(s) listed in the
rfc822Mailbox attribute of the entry.  For example, at U-M my entry has
the attribute

	mail= tim@terminator.rs.itd.umich.edu

So mail sent to tim@umich.edu will be delivered via mail500 to that
address.  If there were multiple values for the mail attribute, multiple
copies of the mail would be sent.

A new object class, rfc822MailGroup, and several new attributes have
been defined to handle email groups/mailing lists.  To use this, you
will need to add this to your local oidtable.oc:

	# object class for representing rfc 822 mailgroups
	rfc822MailGroup:        umichObjectClass.2 : \
		top : \
		cn : \
		rfc822Mailbox, member, memberOfGroup, owner, \
		errorsTo, rfc822ErrorsTo, requestsTo, rfc822RequestsTo,
		joinable, associatedDomain, \
		description, multiLineDescription, \
		userPassword, krbName, \
		telecommunicationAttributeSet, postalAttributeSet

And you will need to add these to your local oidtable.at:

	# attrs for rfc822mailgroups
	multiLineDescription:   umichAttributeType.2    : CaseIgnoreList
	rfc822ErrorsTo:         umichAttributeType.26   : CaseIgnoreIA5String
	rfc822RequestsTo:       umichAttributeType.27   : CaseIgnoreIA5String
	joinable:               umichAttributeType.28   : Boolean
	memberOfGroup:          umichAttributeType.29   : DN
	errorsTo:		umichAttributeType.30	: DN
	requestsTo:		umichAttributeType.31	: DN

The idea was to define a kind of hybrid mail group that could handle
people who were in X.500 or not.  So, for example, members of a group
can be specified via the member attribute (for X.500 members) or the
rfc822MailBox attribute (for non-X.500 members).  Similarly for the
errorsTo and rfc822ErrorsTo, and the requestsTo and rfc822RequestsTo
attributes.

To create a real mailing list, with a list maintainer, all you have to
do is create an rfc822MailGroup and fill in the errorsTo or
rfc822ErrorsTo attributes (or both).  That will cause any errors
encountered when delivering mail to the group to go to the addresses
listed (or X.500 entry via it's mail attribute).

If you fill in the requestsTo or rfc822RequestsTo (or both) attributes,
mail sent to groupname-request will be sent to the addresses listed
there.  mail500 does this automatically, so you don't have to explicitly
add the groupname-request alias to your group.

To allow users to join a group, there is the joinable flag.  If TRUE,
mail500 will search for entries that have a memberOfGroup attribute
equal to the DN of the group, using the same algorithm it used to find
the group in the first place (i.e. the DNs and filters listed in the
base array).  This allows people to join (or subscribe to) a group
without having to modify the group entry directly.  If joinable is
FALSE, the search is not done.

Finally, keep in mind that this is somewhat experimental at the moment.
We are using it in production at U-M, but your mileage may vary...