courieruucp - Sample Courier mail filter
The Courier mail server is capable of sending and receiving mail via
UUCP. Courier does not implement UUCP directly, but instead uses
third-party UUCP software, which you must install separately. Courier´s
UUCP support is provided automatically by the courieruucp module, which
is compiled and installed by default.
Courier sends mail via UUCP by issuing a request via uux to execute the
rmail command on the remote UUCP node. Courier passes the message
envelope sender to rmail via the -f flag, and lists the message
envelope recipients as the remaining arguments. Message envelope
addresses and E-mail addresses in the headers of the message will be
Courier will only send mail via UUCP if it knows about the recipient´s
UUCP node. The configuration file /etc/courier/uucpneighbors is a plain
text configuration file. The makeuucpneighbors script compiles this
configuration file into a binary database that is read by Courier.
Changes to /etc/courier/uucpneighbors do not take effect until
makeuucpneighbors is executed, and Courier is restarted.
/etc/courier/uucpneighbors may also be a subdirectory instead of a
plain text file, in which case the contents of all text files in this
subdirectory is automatically concatenated by the makeuucpneighbors
Contents of /etc/courier/uucpme
This configuration file must be initialized to contain the UUCP node
name that this machine is known to its neighbors. If
/etc/courier/uucpme does not exist, Courier uses the first node name of
the hostname specified by the /etc/courier/me configuration file.
Contents of /etc/courier/uucpneighbors
Note that in addition to creating this configuration file you must also
configure your UUCP software to appropriately route UUCP mail to the
specified nodes, which is a completely separate task. Blank lines in
this file are ignored. Lines that start with the # character are
comments, and are also ignored. The remaining lines are in the
node is a UUCP node, such as "apple" or "food!fruits!apple". <TAB> is a
single tab character, and flags is zero or more of single character
flags described below. The tab character can be ommited if there are no
If there is an entry for node in /etc/courier/uucpneighbors then
Courier will accept mail for any address of the form "node!user", but
not "node!nodule!user". In order to accept mail for "node!nodule!user"
you must enter both "node" and "node!nodule", unless you use the F or
the G flag.
The flags are as follows:
Unrestricted forwarding. This flag will accept any UUCP path that
starts with the specified node. Example:
This will accept "food!fruits!apple", "food!fruits!banana",
"food!drinks!orangejuice", and so on. You may simply list all your
immediate UUCP neighbors using the F flag, and accept mail to any
address that´s reachable via any neighbor.
This is a gateway. This flag is identical to the F flag, except
that rmail is executed on the specified node. Normally, Courier
will issue a uux request to run rmail on the last node, for example
"uux food!fruits!rmail apple". Using G instead of F will run rmail
on the listed node, for example "uux food!rmail fruits!apple".
This is a relay. This flag is used where neither F or G flags are
appropriate, but you want to run rmail on this node. For example:
In this example mail to "food!fruits!apple" is sent by executing
"uux food!rmail fruits!apple". If the R flag is not specified, then
Courier will request "uux food!fruits!rmail apple".
Contents of /etc/courier/module.uucp
This is the standard Courier module configuration file.
Maximum simultaneous UUCP deliveries. This setting is a bit
misleading. From Courier´s viewpoint, a delivery consists only of
running uux to queue up the message via UUCP. Once uux returns, the
message is delivered, as far as Courier is concerned. UUCP is
responsible for getting the message the rest of the way. Therefore,
UUCP deliveries tend to be fairly quick, and it is not necessary to
configure a large number of concurrent courieruucp processes, since
each one will terminate quickly. Once uux terminates, the UUCP
software is responsible for queueing and sending the message.
Maximum simultaneous UUCP deliveries to the same UUCP node. Since
UUCP deliveries tend to be fairly quick, it is not usually
necessary to use MAXHOST to limit concurrent deliveries to the same
UUCP node, so MAXHOST should generally be set to the same value as
Maximum recipients per message. When the same message is sent to
multiple recipients on the same UUCP node, Courier is capable of
asking to run rmail only one, and listing all the recipients
together. MAXRCPT specifies the upper limit on the number of
recipients that are batched together. You want to set a limit based
on any limitations on the length of command lines that´s imposed by
the operating system. Sending the same message to different UUCP
nodes is always handled as separate deliveries.
HEADER AND ADDRESS REWRITING
Courier is certainly capable of relaying mail between the Internet -
via ESMTP - and UUCP-land, rewriting headers and addresses
appropriately. The address rewriting rules are fixed, but they are
expected to work in nearly every case. If you find yourself in some
oddball situation, you´ll just have to invest the time to add custom
header rewriting code.
If you are example.com, and your UUCP node is example, then
<firstname.lastname@example.org> gets rewritten as example!user.
Internet mail may be sent via ESMTP to your UUCP neighbor apple!john by
sending it to <email@example.com>. When that´s forwarded via UUCP
the return address of <firstname.lastname@example.org> will be rewritten as
apple!john will get the mail with this return address, which should be
repliable back to the sender. Courier´s UUCP module will receive the
UUCP address domain.com!someone, and translate it back as
Courier does not support defining multiple UUCP node names in
esmtpd(8), couriertcpd(8), courier(8).