smtp.proxy.1

smtp proxy source code!

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.TH SMTP.PROXY 1 "28 August 1999"
.SH NAME
smtp.proxy \- SMTP proxy server
.SH SYNOPSIS
\fBsmtp.proxy\fR [\fIoptions\fR] [\fIserver\fR]
.SH DESCRIPTION
.I smtp.proxy
is a proxy server for the SMTP protocol.
It forwards traffic between a client and a server watching that the client
fullfills the protocol specification.
.PP
.I smtp.proxy
is usually started from a TCP superserver like
.IR inetd (1)
or
.IR tcpproxy (1).
It can be used from the command line to but does not support binding to a
service port like
.IR sendmail (1).
.PP
\fIserver\fR can be either an SMTP server on a different machine which is then
contacted via TCP/IP or a local \fIsendmail\fR binary.
If \fIserver\fR is omitted the latter is assumed with \fIsendmail\fR
in \fI/usr/sbin\fR.
.SS Protocol Support
.I smtp.proxy
supports the following SMTP commands:
.PP
.RS
HELO, EHLO
.br
[MAIL|SEND|SOML|SAML] FROM, RCPT TO, DATA,
.br
NOOP, RSET, HELP, ETRN, QUIT
.br
.PP
.RE
Unsupported SMTP commands result in a syslog message without forwarding the
command to the server.
ETRN is only supported if the \fB-e\fR option is given on the command line.
.PP
Email addresses are checked againt some simple tests:
.PP
.RS
- they must be enclosed in angle brackets `<', `>',
.br
- they must contain exactly one `@',
.br
- they must not contain a `%' or a `!',
.br
- `:' and `,' characters are also not allowed.
.br
.PP
.RE
While these checks block some valid email addresses they are almost
what you want these days in an Internet with DNS.
.br
The special envelope address `<>' is always allowed.
.SH OPTIONS
The following options are available:
.TP
.B -e
enable proxying of then ETRN command.
.TP
.B -d
switch to debug mode: the dialog between server and client is written to
stderr.
.TP
\fB-l\fR \fIdir\fR
if set \fIsmtp.proxy\fR looks if the file \fIclientip\fR exists in
the directory \fIdir\fR and if it's not older than 600 seconds.
If so the client is accepted otherwise not.
.TP
.B -q
remove the mailpath from the received mail.
Specifing \fb-q\fR twice supresses also the proxy's own `received from' line.
.TP
\fB-r\fR \fIrcptlist\fR
specify a comma separated list of valid receipients.
If this option is set \fIsmtp.proxy\fR checks each receipient from the RCPT
command against the patterns (use `*' and `?' as wildcards) from that list
and rejects it if it doesn't match any pattern without forwarding the
request to the server.
.br
If a pattern from \fIrcptlist\fR starts with an `@'-sign only the domain part
of the email address is matched against it, not the whole email address.
.TP
\fB-s\fR \fIsenderlist\fR
the same as the above \fIrcptlist\fR but for senders in the MAIL command.
.TP
\fB-t\fR \fItimeout\fR
specify a different SMTP timeout in seconds than the default of 300 (5 minutes).
.PP
.SH NOTES
If your running \fIsmtp.proxy\fR with a local \fIsendmail\fR make sure the
user running the proxy is on the \fBT\fIuser\fR list in \fIsendmail.cf\fR.
Otherwise you'll get authentication warnings in your syslog and the emails.
.SH "SEE ALSO"
.IR inetd (1),
.IR sendmail (1),
.IR tcpproxy (1).