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or some similar tool)
as any logical need.
Maintaining more than three separate tables by hand
is essentially an impossible job.
.sh 4 "Small site \*- complete information"
.pp
A small site
(two or three hosts)
may find it more reasonable to have complete information
at each host.
This would require that each host
know exactly where each network connection is,
possibly including the names of each host on that network.
As long as the site remains small
and the the configuration remains relatively static,
the update problem will probably not be too great.
.sh 4 "Single host"
.pp
This is in some sense the trivial case.
The only major issue is trying to insure that you don't
have to know too much about your environment.
For example,
if you have a UUCP connection
you might find it useful to know about the names of hosts
connected directly to you,
but this is really not necessary
since this may be determined from the syntax.
.sh 3 "Relevant issues"
.pp
The canonical form you use
should almost certainly be as specified in
the Arpanet protocols
RFC819 and RFC822.
Copies of these RFC's are included on the
.i sendmail
tape
as
.i doc/rfc819.lpr
and
.i doc/rfc822.lpr .
.pp
RFC822
describes the format of the mail message itself.
.i Sendmail
follows this RFC closely,
to the extent that many of the standards described in this document
can not be changed without changing the code.
In particular,
the following characters have special interpretations:
.(b
< > ( ) " \e
.)b
Any attempt to use these characters for other than their RFC822
purpose in addresses is probably doomed to disaster.
.pp
RFC819
describes the specifics of the domain-based addressing.
This is touched on in RFC822 as well.
Essentially each host is given a name
which is a right-to-left dot qualified pseudo-path
from a distinguished root.
The elements of the path need not be physical hosts;
the domain is logical rather than physical.
For example,
at Berkeley
one legal host is
.q a.cc.berkeley.arpa ;
reading from right to left,
.q arpa
is a top level domain
(related to, but not limited to, the physical Arpanet),
.q berkeley
is both an Arpanet host and a logical domain
which is actually interpreted by
a host called ucbvax
(which is actually just the
.q "major"
host for this domain),
.q cc
represents the Computer Center,
(in this case a strictly logical entity),
and
.q a
is a host in the Computer Center;
this particular host happens to be connected
via berknet,
but other hosts might be connected via one of two ethernets
or some other network.
.pp
Beware when reading RFC819
that there are a number of errors in it.
.sh 3 "How to proceed"
.pp
Once you have decided on a philosophy,
it is worth examining the available configuration tables
to decide if any of them are close enough
to steal major parts of.
Even under the worst of conditions,
there is a fair amount of boiler plate that can be collected safely.
.pp
The next step is to build ruleset three.
This will be the hardest part of the job.
Beware of doing too much to the address in this ruleset,
since anything you do will reflect through
to the message.
In particular,
stripping of local domains is best deferred,
since this can leave you with addresses with no domain spec at all.
Since
.i sendmail
likes to append the sending domain to addresses with no domain,
this can change the semantics of addresses.
Also try to avoid
fully qualifying domains in this ruleset.
Although technically legal,
this can lead to unpleasantly and unnecessarily long addresses
reflected into messages.
The Berkeley configuration files
define ruleset nine
to qualify domain names and strip local domains.
This is called from ruleset zero
to get all addresses into a cleaner form.
.pp
Once you have ruleset three finished,
the other rulesets should be relatively trivial.
If you need hints,
examine the supplied configuration tables.
.sh 3 "Testing the rewriting rules \*- the \-bt flag"
.pp
When you build a configuration table,
you can do a certain amount of testing
using the
.q "test mode"
of
.i sendmail .
For example,
you could invoke
.i sendmail
as:
.(b
sendmail \-bt \-Ctest.cf
.)b
which would read the configuration file
.q test.cf
and enter test mode.
In this mode,
you enter lines of the form:
.(b
rwset address
.)b
where
.i rwset
is the rewriting set you want to use
and
.i address
is an address to apply the set to.
Test mode shows you the steps it takes
as it proceeds,
finally showing you the address it ends up with.
You may use a comma separated list of rwsets
for sequential application of rules to an input;
ruleset three is always applied first.
For example:
.(b
1,21,4 monet:bollard
.)b
first applies ruleset three to the input
.q monet:bollard.
Ruleset one is then applied to the output of ruleset three,
followed similarly by rulesets twenty-one and four.
.pp
If you need more detail,
you can also use the
.q \-d21
flag to turn on more debugging.
For example,
.(b
sendmail \-bt \-d21.99
.)b
turns on an incredible amount of information;
a single word address
is probably going to print out several pages worth of information.
.sh 3 "Building mailer descriptions"
.pp
To add an outgoing mailer to your mail system,
you will have to define the characteristics of the mailer.
.pp
Each mailer must have an internal name.
This can be arbitrary,
except that the names
.q local
and
.q prog
must be defined.
.pp
The pathname of the mailer must be given in the P field.
If this mailer should be accessed via an IPC connection,
use the string
.q [IPC]
instead.
.pp
The F field defines the mailer flags.
You should specify an
.q f
or
.q r
flag to pass the name of the sender as a
.b \-f
or
.b \-r
flag respectively.
These flags are only passed if they were passed to
.i sendmail,
so that mailers that give errors under some circumstances
can be placated.
If the mailer is not picky
you can just specify
.q "\-f $g"
in the argv template.
If the mailer must be called as
.b root
the
.q S
flag should be given;
this will not reset the userid
before calling the mailer\**.
.(f
\**\c
.i Sendmail
must be running setuid to root
for this to work.
.)f
If this mailer is local
(i.e., will perform final delivery
rather than another network hop)
the
.q l
flag should be given.
Quote characters
(backslashes and " marks)
can be stripped from addresses if the
.q s
flag is specified;
if this is not given
they are passed through.
If the mailer is capable of sending to more than one user
on the same host
in a single transaction
the
.q m
flag should be stated.
If this flag is on,
then the argv template containing
.b $u
will be repeated for each unique user
on a given host.
The
.q e
flag will mark the mailer as being
.q expensive,
which will cause
.i sendmail
to defer connection
until a queue run\**.
.(f
\**The
.q c
configuration option must be given
for this to be effective.
.)f
.pp
An unusual case is the
.q C
flag.
This flag applies to the mailer that the message is received from,
rather than the mailer being sent to;
if set,
the domain spec of the sender
(i.e., the
.q @host.domain
part)
is saved
and is appended to any addresses in the message
that do not already contain a domain spec.
For example,
a message of the form:
.(b
From: eric@ucbarpa
To: wnj@monet, mckusick
.)b
will be modified to:
.(b
From: eric@ucbarpa
To: wnj@monet, mckusick@ucbarpa
.)b
.i "if and only if"
the
.q C
flag is defined in the mailer corresponding to
.q eric@ucbarpa.
.pp
Other flags are described
in Appendix C.
.pp
The S and R fields in the mailer description
are per-mailer rewriting sets
to be applied to sender and recipient addresses
respectively.
These are applied after the sending domain is appended
and the general rewriting sets
(numbers one and two)
are applied,
but before the output rewrite
(ruleset four)
is applied.
A typical use is to append the current domain
to addresses that do not already have a domain.
For example,
a header of the form:
.(b
From: eric
.)b
might be changed to be:
.(b
From: eric@ucbarpa
.)b
or
.(b
From: ucbvax!eric
.)b
depending on the domain it is being shipped into.
These sets can also be used
to do special purpose output rewriting
in cooperation with ruleset four.
.pp
The E field defines the string to use
as an end-of-line indication.
A string containing only newline is the default.
The usual backslash escapes
(\er, \en, \ef, \eb)
may be used.
.pp
Finally,
an argv template is given as the E field.
It may have embedded spaces.
If there is no argv with a
.b $u
macro in it,
.i sendmail
will speak SMTP
to the mailer.
If the pathname for this mailer is
.q [IPC],
the argv should be
.(b
IPC $h [ \fIport\fP ]
.)b
where
.i port
is the optional port number
to connect to.
.pp
For example,
the specifications:
.(b
.ta \w'Mlocal, 'u +\w'P=/bin/mail, 'u +\w'F=rlsm, 'u +\w'S=10, 'u +\w'R=20, 'u
Mlocal,	P=/bin/mail,	F=rlsm	S=10,	R=20,	A=mail \-d $u
Mether,	P=[IPC],	F=meC,	S=11,	R=21,	A=IPC $h, M=100000
.)b
specifies a mailer to do local delivery
and a mailer for ethernet delivery.
The first is called
.q local,
is located in the file
.q /bin/mail,
takes a picky
.b \-r
flag,
does local delivery,
quotes should be stripped from addresses,
and multiple users can be delivered at once;
ruleset ten
should be applied to sender addresses in the message
and ruleset twenty
should be applied to recipient addresses;
the argv to send to a message will be the word
.q mail,
the word
.q \-d,
and words containing the name of the receiving user.
If a
.b \-r
flag is inserted
it will be between the words
.q mail
and
.q \-d.
The second mailer is called
.q ether,
it should be connected to via an IPC connection,
it can handle multiple users at once,
connections should be deferred,
and any domain from the sender address
should be appended to any receiver name
without a domain;
sender addresses should be processed by ruleset eleven
and recipient addresses by ruleset twenty-one.
There is a 100,000 byte limit on messages passed through this mailer.
.++ A
.+c "COMMAND LINE FLAGS"
.ba 0
.nr ii 1i
.pp
Arguments must be presented with flags before addresses.
The flags are:
.ip "\-f\ \fIaddr\fP"
The sender's machine address is
.i addr .
This flag is ignored unless the real user
is listed as a
.q "trusted user"
or if
.i addr
contains an exclamation point
(because of certain restrictions in UUCP).
.ip "\-r\ \fIaddr\fP"
An obsolete form of
.b \-f .
.ip "\-h\ \fIcnt\fP"
Sets the
.q "hop count"
to
.i cnt .
This represents the number of times this message has been processed
by
.i sendmail
(to the extent that it is supported by the underlying networks).
.i Cnt
is incremented during processing,
and if it reaches
MAXHOP
(currently 30)
.i sendmail
throws away the message with an error.
.ip \-F\fIname\fP
Sets the full name of this user to
.i name .
.ip \-n
Don't do aliasing or forwarding.
.ip \-t
Read the header for
.q To: ,
.q Cc: ,
and
.q Bcc:
lines, and send to everyone listed in those lists.
The
.q Bcc:
line will be deleted before sending.
Any addresses in the argument vector will be deleted
from the send list.
.ip \-b\fIx\fP
Set operation mode to
.i x .
Operation modes are:
.(b
.ta 4n
m	Deliver mail (default)
a	Run in arpanet mode (see below)
s	Speak SMTP on input side
d	Run as a daemon
t	Run in test mode
v	Just verify addresses, don't collect or deliver
i	Initialize the alias database
p	Print the mail queue
z	Freeze the configuration file
.)b
The special processing for the
ARPANET
includes reading the
.q "From:"
line from the header to find the sender,
printing
ARPANET
style messages
(preceded by three digit reply codes for compatibility with
the FTP protocol
[Neigus73, Postel74, Postel77]),
and ending lines of error messages with <CRLF>.
.ip \-q\fItime\fP
Try to process the queued up mail.
If the time is given,
a sendmail will run through the queue at the specified interval
to deliver queued mail;
otherwise, it only runs once.
.ip \-C\fIfile\fP
Use a different configuration file.
.ip \-d\fIlevel\fP
Set debugging level.
.ip \-o\fIx\|value\fP
Set option
.i x
to the specified
.i value .
These options are described in Appendix B.
.pp
There are a number of options that may be specified as
primitive flags
(provided for compatibility with
.i delivermail ).
These are the e, i, m, and v options.
Also,
the f option
may be specified as the
.b \-s
flag.
.+c "CONFIGURATION OPTIONS"
.pp
The following options may be set using the
.b \-o
flag on the command line
or the
.b O
line in the configuration file:
.nr ii 1i
.ip A\fIfile\fP
Use the named
.i file
as the alias file.
If no file is specified,
use
.i aliases
in the current directory.
.ip a
If set,
wait for an
.q @:@
entry to exist in the alias database
before starting up.
If it does not appear in five minutes,
rebuild the database.
.ip c
If an outgoing mailer is marked as being expensive,
don't connect immediately.
This requires that queueing be compiled in,
since it will depend on a queue run process to
actually send the mail.
.ip d\fIx\fP
Deliver in mode
.i x .
Legal modes are:
.(b
.ta 4n
i	Deliver interactively (synchronously)
b	Deliver in background (asynchronously)
q	Just queue the message (deliver during queue run)
.)b
.ip D
If set,
rebuild the alias database if necessary and possible.
If this option is not set,
.i sendmail
will never rebuild the alias database
unless explicitly requested
using
.b \-bi .
.ip e\fIx\fP
Dispose of errors using mode
.i x .
The values for
.i x
are:
.(b
p	Print error messages (default)
q	No messages, just give exit status
m	Mail back errors
w	Write back errors (mail if user not logged in)
e	Mail back errors and give ze