smtpd

README

Go smtpd

Package smtpd implements an SMTP server in golang.

Moved to Github

I have moved development to Github where future development will take place.

Documentation

Overview

Package smtpd implements an SMTP server with support for STARTTLS, authentication (PLAIN/LOGIN), XCLIENT and optional restrictions on the different stages of the SMTP session.

Index

• type Envelope
  • func (env *Envelope) AddReceivedLine(peer Peer)
• type Error
  • func (e Error) Error() string
• type Peer
• type Protocol
• type Server
  • func (srv *Server) ListenAndServe(addr string) error
  • func (srv *Server) Serve(l net.Listener) error

Examples

• Server

Types

type Envelope

type Envelope struct {
	Sender     string
	Recipients []string
	Data       []byte
}

Envelope holds a message

func (*Envelope) AddReceivedLine

func (env *Envelope) AddReceivedLine(peer Peer)

AddReceivedLine prepends a Received header to the Data

type Error

type Error struct {
	Code    int    // The integer error code
	Message string // The error message
}

Error represents an Error reported in the SMTP session.

func (Error) Error

func (e Error) Error() string

Error returns a string representation of the SMTP error

type Peer

type Peer struct {
	HeloName   string               // Server name used in HELO/EHLO command
	Username   string               // Username from authentication, if authenticated
	Password   string               // Password from authentication, if authenticated
	Protocol   Protocol             // Protocol used, SMTP or ESMTP
	ServerName string               // A copy of Server.Hostname
	Addr       net.Addr             // Network address
	TLS        *tls.ConnectionState // TLS Connection details, if on TLS
}

Peer represents the client connecting to the server

type Protocol

type Protocol string

Protocol represents the protocol used in the SMTP session

const (
	SMTP  Protocol = "SMTP"
	ESMTP          = "ESMTP"
)

type Server

type Server struct {
	Hostname       string // Server hostname. (default: "localhost.localdomain")
	WelcomeMessage string // Initial server banner. (default: "<hostname> ESMTP ready.")

	ReadTimeout  time.Duration // Socket timeout for read operations. (default: 60s)
	WriteTimeout time.Duration // Socket timeout for write operations. (default: 60s)
	DataTimeout  time.Duration // Socket timeout for DATA command (default: 5m)

	MaxConnections int // Max concurrent connections, use -1 to disable. (default: 100)
	MaxMessageSize int // Max message size in bytes. (default: 10240000)
	MaxRecipients  int // Max RCPT TO calls for each envelope. (default: 100)

	// New e-mails are handed off to this function.
	// Can be left empty for a NOOP server.
	// If an error is returned, it will be reported in the SMTP session.
	Handler func(peer Peer, env Envelope) error

	// Enable various checks during the SMTP session.
	// Can be left empty for no restrictions.
	// If an error is returned, it will be reported in the SMTP session.
	// Use the Error struct for access to error codes.
	ConnectionChecker func(peer Peer) error              // Called upon new connection.
	HeloChecker       func(peer Peer, name string) error // Called after HELO/EHLO.
	SenderChecker     func(peer Peer, addr string) error // Called after MAIL FROM.
	RecipientChecker  func(peer Peer, addr string) error // Called after each RCPT TO.

	// Enable PLAIN/LOGIN authentication, only available after STARTTLS.
	// Can be left empty for no authentication support.
	Authenticator func(peer Peer, username, password string) error

	EnableXCLIENT       bool // Enable XCLIENT support (default: false)
	EnableProxyProtocol bool // Enable proxy protocol support (default: false)

	TLSConfig *tls.Config // Enable STARTTLS support.
	ForceTLS  bool        // Force STARTTLS usage.

	ProtocolLogger *log.Logger
}

Server defines the parameters for running the SMTP server

Example

package main

import (
	"bitbucket.org/chrj/smtpd"
	"errors"
	"net/smtp"
	"strings"
)

func main() {
	var server *smtpd.Server

	// No-op server. Accepts and discards
	server = &smtpd.Server{}
	server.ListenAndServe("127.0.0.1:10025")

	// Relay server. Accepts only from single IP address and forwards using the Gmail smtp
	server = &smtpd.Server{

		HeloChecker: func(peer smtpd.Peer, name string) error {
			if !strings.HasPrefix(peer.Addr.String(), "42.42.42.42:") {
				return errors.New("Denied")
			}
			return nil
		},

		Handler: func(peer smtpd.Peer, env smtpd.Envelope) error {

			return smtp.SendMail(
				"smtp.gmail.com:587",
				smtp.PlainAuth(
					"",
					"username@gmail.com",
					"password",
					"smtp.gmail.com",
				),
				env.Sender,
				env.Recipients,
				env.Data,
			)

		},
	}

	server.ListenAndServe("127.0.0.1:10025")
}

func (*Server) ListenAndServe

func (srv *Server) ListenAndServe(addr string) error

ListenAndServe starts the SMTP server and listens on the address provided

func (*Server) Serve

func (srv *Server) Serve(l net.Listener) error

Serve starts the SMTP server and listens on the Listener provided