umdss - Unix Mail Delivery SubSystem


umdss [ site ]
umdss -q
umdss -v


Command line option -q queries umdss to report information on traffic pending for each site, including live connections. The -v option displays the umdss version and copyright information. With no arguments, umdss prepares for a remote site to log in and begin a session. With a site argument, umdss begins a session for a site that has just been polled (originate mode) and is connected. (Polling is not part of the umdss software).


This document describes the umdss program that runs on UNIX computers, providing a compatible mail exchange interface with ProLine systems. It is organized into the following sections:

o About UMDSS
o How it Works
o Account Installation
o Installing UMDSS
o File Permissions and Directories
o ProLine Site Installation
o Transporting Mail
o Transporting Mail with Shell Scripts
o Transporting News
o For the ProLine Administrator
o Logfile
o Job and Session Reports


Umdss is a simple mail exchange program. It implements the Mail Delivery Subsystem (MDSS) protocol designed in 1985 by Morgan Davis and Bill Blue for the purpose of simplifying the exchange of mail and news with microcomputers, like the Apple II.

Here are some of umdss’s features:

o Mimics UUCP in many ways.
o Maintains site lock (LCK) files.
o Updates session “.Status” files.
o Includes a uustat-like function (the -q option).
o Integrates with the local mail system (works best with smail 3.x).
o Maintains a detailed log file.
o Includes a large packet protocol (mdx) for 90-95% transfer efficiency.
o Supports non-batched external protocols as well (e.g. sx/rx).
o Compatible with high-speed modems and ports.

Note that umdss is simply a mail tranportation utility. It does not possess the ability to dial a remote host, connect, and login. A separate utility could accomplish this, then invoke umdss (with the name of the site being called as an argument).

How It Works

A ProLine system dials into the UNIX machine to login as “umdss”. This runs the umdss program (with no arguments). The ProLine system is initially the master, commanding the UNIX machine (the slave) to receive mail (if there is any). When all mail is sent, the two machines reverse roles; the UNIX side becomes master, and ProLine, the slave. Again, the master commands the slave to receive mail (if there is any).

When a letter is sent, umdss calls upon an external file transfer program to transmit the file. Umdss deletes each file successfully sent, and places an entry in the umdsslog file.

Likewise, when a letter is received, umdss runs a transfer utility to receive the file, then mails it through rmail. When rmail is done, umdss logs the reception of the letter.

Among other things, log entries show the site, date, time, size and recipient of each letter. (See the “Logfile” section for more details).

Finally, when all mail is exchanged, both machines disconnect.

Account Installation

The first step is to create an account with the following attributes:

Login: umdss Password: whatever Home: /usr/local/lib/umdss Shell: /usr/local/lib/umdss/umdss Aging: Disabled -- the account should never expire.

While you’re at it, set up a mail alias so that any incoming messages addressed to “umdss” (i.e. bounces from the net) are sent to a legitimate administrative account.

You should include umdss in the same group as “uucp”.

Installing UMDSS

The umdss package, normally distrbuted as a compressed tar file, includes C source code, utilities, and support files for running umdss on a UNIX computer.

Follow these steps to install the UMDSS package (it is assumed that you have sufficient access to create directories and accounts on the system):


Uncompress umdss.tar.Z (e.g. uncompress umdss.tar.Z)


Change directories to /usr/local/lib (e.g. cd /usr/local/lib). (The recommended location is in the /usr/local/lib hierarchy. This location is used throughout this document).


Unarchive the tar file (e.g. tar xvf umdss.tar). Older versions of tar may require the “o” option to create the extracted files using your group ID information.

The /usr/local/lib directory now includes the umdss directory which contains the following files:

README This document in plain text format README.mdx Plain text MDX documentation This document in PostScript format idfile.sample Sample ID file promail* Mail grabbing script promail.bsd* Mail grabbing script for BSD query.proline* Sample smail query script smroute Sample smail routers entry smtrans Sample smail transports entry src/ Source code directory with Makefile

To build the umdss utility programs, change directories to “src”. The source code has been written to be compatible with most popular systems (XENIX, SCO UNIX, Interactive UNIX, and BSD systems). However, some tweaks may be necessary to accomodate your system.

Before building the executables, take a look at the “config.h” file. You will want to read the introductory comments and make changes to it as required by your system.

When ready, issue the “make” command. This begins the compilation process on the source files, and if all goes well, three programs are created: umdss, mdx, and upmail. If any errors are reported, you will have to do some debugging, or enlist a guru to get it to build for your system.

To place the executables in the right spot (the parent directory), use “make install”. To quickly remove the “.o” files, use “make clean” (or “make Clean” with a capital C to remove the redundant executables and object files). Then change directories to “..” to put you back in /usr/local/lib/umdss.

File Permissions and Directories

Make sure that /usr/local/lib/umdss and its files are owned by umdss and are in the right group with appropriate permission modes.

Now you must make the umdss spool directory. This is the directory into which outgoing mail is stored for each ProLine system (each site gets its own directory). The recommended directory is /usr/spool/umdss, should be owned by umdss and be in the uucp group. Individual site directories will be created automatically by umdss, or by the local mail system, so the directory should allow for creation of additional directories by umdss.

Verify that “idfile” has appropriate permissions set so that it can be read only by umdss.

Umdss creates lock files (e.g. in the appropriate directory where UUCP stores its lock files. Make sure umdss has the ability to write to this directory.

Before you can send mail to a ProLine site, inform the UNIX mail system of the site’s existence, ensuring that the system never dials the ProLine site. This involves editing the Systems (or L.sys) file and paths database. The procedure may differ among brands of UNIX.

ProLine Site Installaton

Perform the following steps for each ProLine site that will have access to the umdss account:

Add an entry into the “idfile” (or edit the sample entry provided if this is your first time). The format of the idfile is as follows:


Pro-site is the name of the ProLine site (e.g. pro-apple2). Password is a security code that the ProLine site sends to verify its identity. The send-command and receive-command items are command lines that invoke the external protocol programs to exchange mail. Example:

pro-sol;morgan;mdx -L -s %s;mdx -L -r %s

This example shows that the mdx program is used for both sending and receiving. The %s characters indicate where the protocol program expects a filename. (See the “README.mdx” file for details on using mdx’s options).

Note: The mdx program is invoked via the C function system(). Some UNIX implementations do not include the current directory in the executable search path. You may have to add “./” (e.g. “./mdx”) for mdx to be found and executed by system().

The “idfile” may include comments where desired. Comments follow the pound-sign (#) character.

Transporting Mail

If the UNIX host is running a smart mailer, like smail version 3.x or newer, it can be told to deposit messages directly into ProLine site directories. This is done by integrating the upmail transport program with smail. It takes a little work to get it set up, but it is far more efficient to use than any other scheme.

You should be familiar with smail’s transport and routing feature. The “transports” file is used to tell smail how to call a transport program like upmail. (Umdss comes with a sample entry for the transports file in “smtrans”.)

The “routers” file tells smail how to recognize which sites use a particular transport. Two entries are needed so that smail can locate directly connected ProLine sites as well as any ProLine sites found in a “” database containing the paths to known ProLine systems. (A sample routers entry can be found in “smroute”.)

Smail uses a query script to find out which router to use when delivering mail. (Umdss comes with a sample shell script named “query.proline”.) By default, this script reads the umdss idfile to match directly connected ProLine systems (this means the idfile must be able to be read by smail). A more secure and more efficient scheme is to create a list of directly connected sites in the script’s “for” loop. The drawback to this approach is that you need to remember to edit the script each time you add or remove a directly connected site.

A working example is described as follows: two routers are designated to any sites that begin with “pro-”. They test the addresses before local and paths matching for regular traffic. The first one looks for exact matches (first hop) using the query.proline script. This script scans umdss’s idfile for names that are directly connected to the host. If that fails, the next test uses a sorted paths-formatted database and lookup to resolve any path that involves a ProLine site.

(That database is made by using grep, searching for “<tab>pro-” in the master paths database and saving the results to The reason for this is so that any target ProLine site can be recognized and use the upmail transport, rather than the uux transport that would be used if there was a match in paths, which is the next test if this one fails.)

Obviously, the logic utilized to make this all work (with gateway resolution) would vary dramatically according to the mail transport. You may also need to make adjustments to the sample files if your directories differ.

Transporting Mail with Shell Scripts

If the UNIX host doesn’t have a flexible mailer, like the kind described above, the umdss package includes a shell script called “promail” (and “promail.bsd” for use on BSD systems). Promail is run by either “root” or “uucp” to move mail in a ProLine site’s UUCP directory (e.g., /usr/spool/uucp/pro-site) into the spool directory where umdss expects it (/usr/spool/umdss/pro-site). Control and execution files are deleted, and only the actual data files (those containing mail) are moved out of the UUCP area, into the umdss spool area for the corresponding site.

If you have to use the shell scripts, add an entry in a crontab file to execute “promail” (or “promail.bsd”) as often as traffic demands. The script should be run via root or uucp, and requires at least one argument: the name of the ProLine site. Example:

20 * * * * /bin/su -c "/usr/umdss/promail pro-site" >/dev/null 2>&1

Older UNIX systems may impose a length restriction on site names. If this is the case with your system, and the site you’re adding has a name that exceeds the limit, add a second name argument: the truncated version of the ProLine site’s name. For example, if the site is called pro-apple2, and your machine imposes an eight character restriction, give “pro-appl” as the second argument.

Modern UNIX systems can accomodate all ProLine site names which are usually less than 12 characters, but never exceed 15.

Transporting News

The cnews program makes it easy to send uncompressed news batches through the mail system to a ProLine site. Be sure that the batches are NOT compressed and that they are sent via mail (not deposited directly into the ProLine site directories). The batches should be addressed to the ProLine site’s rnews account (e.g., pro-site!rnews).

For the ProLine Administrator

UNIX administrators will want to pass this information onto sites that will poll it:

The ProLine administrator should take appropriate steps to connect with the UNIX machine by invoking its mdss program with options that agree with the protocol being used on the UNIX system. If mdx is used with the -L (4K XMODEM) option, the ProLine site will invoke mdss with “-x TLX” after connecting. This tells it to enable text (newline) conversion, large 4K packets, and standard XMODEM.

A typical L.sys entry for ProLine systems might look like this:

unix-host Any 9600 593-7305|593-6481 local \[in:]2-^M;-[in:]5 umdss \[rd:] whatever \[id:] pro-site;password \!"mdss -x TLX unix-host"

If the ProLine system is running CS 2.7a or newer, news articles to be posted to the net should be addressed to rnews (e.g. rnews@host). Otherwise, the UNIX administrator may want to set up some aliases that redirect e-mail letters into specific newsgroups. Again, this is very easy to do with cnews.


Umdss maintains a log file of all messages received and sent, including connect and disconnect information. (NOTE: Umdss can only create the log file if the umdss home directory is owned by umdss, or if a mdsslog file is manually created with proper permissions set).

Here is a sample section from the umdsslog file:

pro-sol 8/30-10:28 C i1F 38400 pro-sol 8/30-10:28 R 1636!mporter pro-sol 8/30-10:28 R 734!tfschmidt pro-sol 8/30-10:29 R 2041 pnet01!crash!!mlg pro-sol 8/30-10:29 S 4656 rnews pro-sol 8/30-10:29 S 1914 mdavis pro-sol 8/30-10:29 S 1563 rnews pro-sol 8/30-10:29 S 3407 mdavis pro-sol 8/30-10:29 H S#4,11540 R#3,4411 i1F 38400

Each entry begins with the site’s name and the current date and time. Entry codes are:


Connection (showing the port and speed)


Receive (with byte count and target address)


Send (with byte count and target address)


Hangup (showing transfer summaries, port, and speed)


ALERT or ERROR message


Debugging message

The H entry shows the number of files (and total bytes) sent after the S#, and the number of files received (and total bytes) after the R#.

The umdsslog file can grow quickly, depending on traffic, and requires occassional attention. Using grep to find lines containing “*” is useful for quickly spotting errors.

Jobs and Session Reports

The -q option reports current information about all ProLine sites serviced by umdss:

Site Jobs Kilobytes Last Access TTY Session =============== ==== ========= =========== === ======= pro-acsd 7 12.30 09/17-06:50 i1A success pro-amber 4 165.12 09/19-15:55 i1D success pro-angmar 4 7.29 09/19-00:24 i1G success pro-beagle 0 0.00 09/19-16:14 i1D success pro-calgary 5 8.23 09/19-02:43 i1D success pro-carolina 6 35.99 09/19-17:25 i1D TALKING Received 5 (250K) pro-nbs 3 7.56 09/19-14:36 i1F success pro-nsdapple 3 21.18 09/19-14:55 i1E success pro-party 1 25.15 09/19-16:00 i1E success pro-sat 10 142.68 09/19-04:04 i1D success pro-sol 34 149.33 09/19-17:19 i1M TALKING =============== ==== ========= =========== === ======= 77 574.81

The -q option will report FAILED sessions as well as bogus lock (LCK) files that would otherwise indicate active sessions. Bogus locks can occur if umdss terminates abnormally, but they won’t prevent subsequent sessions from starting up.


The umdss project is continually evolving as new UNIX systems implement it. Comments are appreciated on the software (and documentation) and any suggestions for making it work better.

If you make changes to the source code, be sure to enclose them within conditional directives. Do not change any of the existing code. Send your changes to so they can be included in the next official distribution.


umdss’s home,
site id file,
source code directory,
site spool directories,
contains site’s status files

See Also (ProLine)

intro(NET), poll(NET), scan(NET), sendmail(C)

See Also (Unix)

cnews(C), smail(C)


Morgan Davis ( and Bill Blue (