AT&T Gateway Administration Guide

The interface to AT&T mail is the UUCP protocol, and so the AT&T gateway must have a UUCP link to the AT&T mail hub available. Due to the binary nature of AT&T mail, the conversion processes must run on the machine with the UUCP link as the binary data cannot be reliably carried around an SMTP network without further encoding.

Machine Requirements

The gateway requires the following to be available:

SMTP configured
UUCP link to AT&T mail
AT&T mail account
Less than 1Mbyte of space for the executables
Space for spooling conversion files

SMTP configuration

SMTP must be configured to allow mail of the format @attmail.uucp to be sent across a local UUCP link to the site attmail. SMTP should also be configured to append @attmail.uucp to any mail coming from the UUCP link.

UUCP configuration

The software has been tested with Taylor UUCP 1.05, although all UUCP software should work. AT&T mail accepts "smart" (multi-recipient) UUCP, but always sends items using original UUCP. This means that items for multiple receipients are:

sent across the UUCP link
coverted by the gateway
sent across SMTP

once for each recipient. This is slow for large items sent to multiple recipients. The UUCP nodename should be configured in accordance with the details of the AT&T mail account.

AT&T mail account

An account must be configured in the local AT&T mail hub to allow UUCP transfers to occur. This account must be configured as a Unix style account. This account type allows mail to be queued for UUCP collection and allows external mail to be injected via UUCP. The Telstra AT&T mail account name is telstra with AT&T Sydney.

Directory Structure

The AT&T mail gateway consists of a number of executables and spool directories. The spool directories store the temporary input and output files, which allows failed conversions to be kept and examined for further processing. The executables work with the UUCP and sendmail programs to allow the transfer and conversion of mail between SMTP and AT&T mail.

The directory structure can be moved to any filesystem with suitable disk space, but is commonly installed under /var/spool/attmail. The executables are run from sendmail and the UUCP programs rmail and uux, and so are run in a set-uid environment. The executables are written in PERL, and set-uid wrappers are used to avoid kernel set-uid problems, which means that the pathnames to the executables must be fixed at install time.

The following sub-directories are used:

Directory	Usage
bin	Executable scripts, called from rmail and uux
rmail/input	Input file seen by rmail in AT&T format
rmail/output	Output file from conversion to SMTP format
uux/input	Input file seen by uux in SMTP format
uux/output	Output file from conversion to AT&T mail format
log/smtp2att.log	Log file of conversion from SMTP to AT&T mail
log/att2smtp.log	Log file of conversion from AT&T mail to SMTP

In addition, the following system files need to be modified:

System File	Modifications required
/usr/bin/uux	Renamed to uux.bin and replaced with a shell wrapper
/usr/bin/rmail	Renamed to rmail.bin and replaced with a shell wrapper
/etc/sendmail.cf	Modified to support UUCP link to AT&T mail

The uux and rmail executables must be replaced with wrapper programs to enable the conversion programs to be called. The AT&T mail binary format cannot be passed to sendmail, and so the replacement of rmail is required. The conversion to AT&T mail could be performed as a new mailer under sendmail, but is performed through a wrapper around uux to minimise the sendmail changes required and to provide a consistent view of both conversions.

The conversion programs make no attempt to deliver mail, they are purely placed in the sequence of commands executed between the UUCP link and the mail delivery system.

The gateway expects mail for AT&T mail to be addressed to the attmail.uucp domain, and modifies incoming mail to add this domain for replies. The SMTP network should be configured to deliver mail for the attmail.uucp domain to the gateway.

Maintenance

The gateway is designed to be maintenance free. Entries are added to root's crontab file to:

Rotate the uucp log file
Rotate the smtp2att.log and att2smtp.log files
Remove old temporary files
Mail the previous day's logs to a knowledgable user

The rotate_log program is used to perform the log rotation, and is installed as part of the package in /var/spool/attmail/bin/rotate_log.

Mail from SMTP to AT&T mail

This mail is received by the mail delivery system (typically sendmail), and then passed off to uux for delivery across the UUCP link. The gateway replaces uux with a wrapper which converts the mail from the SMTP text format to the AT&T mail binary format, and then calls the original uux executable (renamed as uux.bin) for delivery to UUCP. The uux script:

Copies the input to a file in /var/spool/attmail/uux/input
Calls the smtp2att conversion routine. If this is successful, a file of the same name is created in /var/spool/attmail/uux/output
For successful conversions, calls the uux.bin script, passing the converted file as input.
For failed conversions, errors are logged to smtp2att.log and uux.bin is not called.

Mail from AT&T mail to SMTP

The mail is received by UUCP and then passed to rmail for delivery. The rmail executable is renamed to rmail.bin and replaced with a wrapper which:

Copies the input to a file in /var/spool/attmail/rmail/input
Calls the att2smtp conversion routine. If this is successful, a file of the same name is created in /var/spool/attmail/rmail/output
For successful conversions, calls the rmail.bin script, passing the converted file as input.
For failed conversions, errors are logged to att2smtp.log and rmail.bin is not called.