smtpproxy is a small Go program that accepts messages on port 25 and
relays them directly to a relay host, without local storage. This is
useful for forwarding your own e-mail addresses to gmail or similar
services. smtpproxy also does some minimal spam detection.
smtpproxy is best run from systemd. It uses environment variables
for configuration. See example/defaults for the
list of supported options.
go get github.com/michelvocks/smtpproxy
cp $GOPATH/bin/smtpproxy /usr/local/sbin/
cp $GOPATH/src/github.com/michelvocks/smtpproxy/example/smtpproxy.service \
$GOPATH/src/github.com/michelvocks/smtpproxy/example/smtpproxy.socket \
/etc/systemd/system/
cp $GOPATH/src/github.com/michelvocks/smtpproxy/example/defaults \
/etc/default/smtpproxy
systemctl daemon-reload
$EDITOR /etc/default/smtpproxy
systemctl start smtpproxy.socket
- No local spool or storage at all. The client only receives a success message when the upstream server accepts the mail.
- Minimum implementation as per
RFC 5321 section 4.5.1, with
the exception of
VRFY. - The
STARTTLSextension is supported. - DNSBL/RBL checks are supported
- Delayed welcome: The 220 welcome message is sent with a short delay. If the client speaks before its turn, it is tarpitted. This catches a surprising amount of spammers.
- Tarpit: When a client misbehaves in a bad way, the connection is kept open for some time to slow down spammers.
Contributions are welcome. Please do make sure tests run successfully.
There’s a ./scripts/test command to run the test suite. When adding
code, please try to include tests as well.
This is my first Go program. (Helpful) suggestions for improving the code are very welcome.