courieruucp — Sample Courier mail filter
makeuucpneighbors
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
appropriately rewritten.
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
script.
/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.
/etc/courier/uucpneighborsNote 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 following format:
node<TAB>flags
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 flags.
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:
food<TAB>F
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:
food!fruits food<TAB>R
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".
/etc/courier/module.uucpThis 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 MAXDELS.
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.
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 <user@example.com> gets rewritten as
example!user.
Internet mail may be sent via ESMTP to your UUCP neighbor
apple!john by sending it to <apple!john@example.com>.
When that's forwarded via UUCP the return address of
<someone@domain.com> will be rewritten as
example!domain.com!someone.
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
<someone@domain.com>.