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Sleet is an SMTP server with support for the POP3 protocol.


  • Java 6
  • Maven 2 or greater (to build)


Do a Maven package:

mvn package


  1. Edit "dist/sleet/bin/" to use the host name of your server ("--hostName" argument).
  2. cd dist/sleet/bin
  3. chmod 744
  4. ./

The script will start the Sleet SMTP server on port 2550. Mail submission will run on port 2551 and POP3 will run on port 2552. The reason why these non-standard ports are used is that I couldn't open connections to the standard ports on my computer (ports 25, 587, and 110 respectively). To test it out, you can connect to it via telnet:

telnet localhost <port>


The main class, sleet.Sleet, takes a number of command-line arguments. All arguments are in "long form" for readability.

The SMTP server port (defaults to 25).

The SMTP mail submission port (defaults to 587).

The POP3 server port (defaults to 110).

The Sleet admin console port (defaults to 2553).

--host-name=NAME [required]
The host name of this server (e.g.
This is what's used in email addresses destined for and coming from this server.

The path to where the database will be stored or "MEM" to use an in-memory
database (defaults to "sleet-db").

The path to where inbound SMTP transactions are logged.

The path to where outbound SMTP transactions are logged.

The path to where inbound SMTP mail submission transactions are logged.

The path to where POP3 transactions are logged.

The path to where Sleet admin console transactions are logged.

Prints the version.

Prints this help message.


An SMTP server written in Java.



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