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747 |
jeremybenn |
// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package smtp implements the Simple Mail Transfer Protocol as defined in RFC 5321.
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// It also implements the following extensions:
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// 8BITMIME RFC 1652
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// AUTH RFC 2554
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// STARTTLS RFC 3207
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// Additional extensions may be handled by clients.
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package smtp
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import (
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"crypto/tls"
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"encoding/base64"
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"io"
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"net"
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"net/textproto"
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"strings"
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)
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// A Client represents a client connection to an SMTP server.
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type Client struct {
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// Text is the textproto.Conn used by the Client. It is exported to allow for
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// clients to add extensions.
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Text *textproto.Conn
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// keep a reference to the connection so it can be used to create a TLS
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// connection later
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conn net.Conn
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// whether the Client is using TLS
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tls bool
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serverName string
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// map of supported extensions
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ext map[string]string
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// supported auth mechanisms
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auth []string
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}
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// Dial returns a new Client connected to an SMTP server at addr.
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func Dial(addr string) (*Client, error) {
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conn, err := net.Dial("tcp", addr)
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if err != nil {
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return nil, err
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}
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host := addr[:strings.Index(addr, ":")]
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return NewClient(conn, host)
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}
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// NewClient returns a new Client using an existing connection and host as a
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// server name to be used when authenticating.
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func NewClient(conn net.Conn, host string) (*Client, error) {
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text := textproto.NewConn(conn)
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_, msg, err := text.ReadResponse(220)
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if err != nil {
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text.Close()
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return nil, err
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}
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c := &Client{Text: text, conn: conn, serverName: host}
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if strings.Contains(msg, "ESMTP") {
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err = c.ehlo()
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} else {
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err = c.helo()
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}
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return c, err
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}
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// cmd is a convenience function that sends a command and returns the response
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func (c *Client) cmd(expectCode int, format string, args ...interface{}) (int, string, error) {
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id, err := c.Text.Cmd(format, args...)
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if err != nil {
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return 0, "", err
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}
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c.Text.StartResponse(id)
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defer c.Text.EndResponse(id)
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code, msg, err := c.Text.ReadResponse(expectCode)
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return code, msg, err
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}
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// helo sends the HELO greeting to the server. It should be used only when the
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// server does not support ehlo.
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func (c *Client) helo() error {
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c.ext = nil
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_, _, err := c.cmd(250, "HELO localhost")
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return err
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}
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// ehlo sends the EHLO (extended hello) greeting to the server. It
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// should be the preferred greeting for servers that support it.
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func (c *Client) ehlo() error {
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_, msg, err := c.cmd(250, "EHLO localhost")
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if err != nil {
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return err
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}
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ext := make(map[string]string)
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extList := strings.Split(msg, "\n")
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if len(extList) > 1 {
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extList = extList[1:]
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for _, line := range extList {
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args := strings.SplitN(line, " ", 2)
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if len(args) > 1 {
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ext[args[0]] = args[1]
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} else {
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ext[args[0]] = ""
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}
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}
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}
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if mechs, ok := ext["AUTH"]; ok {
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c.auth = strings.Split(mechs, " ")
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}
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c.ext = ext
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return err
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}
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// StartTLS sends the STARTTLS command and encrypts all further communication.
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// Only servers that advertise the STARTTLS extension support this function.
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func (c *Client) StartTLS(config *tls.Config) error {
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_, _, err := c.cmd(220, "STARTTLS")
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if err != nil {
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return err
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}
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c.conn = tls.Client(c.conn, config)
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c.Text = textproto.NewConn(c.conn)
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c.tls = true
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return c.ehlo()
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}
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// Verify checks the validity of an email address on the server.
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// If Verify returns nil, the address is valid. A non-nil return
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// does not necessarily indicate an invalid address. Many servers
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// will not verify addresses for security reasons.
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func (c *Client) Verify(addr string) error {
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_, _, err := c.cmd(250, "VRFY %s", addr)
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return err
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}
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// Auth authenticates a client using the provided authentication mechanism.
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// A failed authentication closes the connection.
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// Only servers that advertise the AUTH extension support this function.
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func (c *Client) Auth(a Auth) error {
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encoding := base64.StdEncoding
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mech, resp, err := a.Start(&ServerInfo{c.serverName, c.tls, c.auth})
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if err != nil {
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c.Quit()
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return err
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}
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resp64 := make([]byte, encoding.EncodedLen(len(resp)))
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encoding.Encode(resp64, resp)
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code, msg64, err := c.cmd(0, "AUTH %s %s", mech, resp64)
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for err == nil {
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var msg []byte
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switch code {
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case 334:
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msg, err = encoding.DecodeString(msg64)
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case 235:
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// the last message isn't base64 because it isn't a challenge
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msg = []byte(msg64)
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default:
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err = &textproto.Error{Code: code, Msg: msg64}
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}
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resp, err = a.Next(msg, code == 334)
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if err != nil {
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// abort the AUTH
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c.cmd(501, "*")
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c.Quit()
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break
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}
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if resp == nil {
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break
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}
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resp64 = make([]byte, encoding.EncodedLen(len(resp)))
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encoding.Encode(resp64, resp)
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code, msg64, err = c.cmd(0, string(resp64))
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}
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return err
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}
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// Mail issues a MAIL command to the server using the provided email address.
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// If the server supports the 8BITMIME extension, Mail adds the BODY=8BITMIME
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// parameter.
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// This initiates a mail transaction and is followed by one or more Rcpt calls.
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func (c *Client) Mail(from string) error {
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cmdStr := "MAIL FROM:<%s>"
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if c.ext != nil {
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if _, ok := c.ext["8BITMIME"]; ok {
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cmdStr += " BODY=8BITMIME"
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}
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}
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_, _, err := c.cmd(250, cmdStr, from)
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return err
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}
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// Rcpt issues a RCPT command to the server using the provided email address.
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// A call to Rcpt must be preceded by a call to Mail and may be followed by
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// a Data call or another Rcpt call.
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func (c *Client) Rcpt(to string) error {
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_, _, err := c.cmd(25, "RCPT TO:<%s>", to)
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return err
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}
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type dataCloser struct {
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c *Client
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io.WriteCloser
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}
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func (d *dataCloser) Close() error {
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d.WriteCloser.Close()
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_, _, err := d.c.Text.ReadResponse(250)
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return err
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}
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// Data issues a DATA command to the server and returns a writer that
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// can be used to write the data. The caller should close the writer
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// before calling any more methods on c.
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// A call to Data must be preceded by one or more calls to Rcpt.
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func (c *Client) Data() (io.WriteCloser, error) {
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_, _, err := c.cmd(354, "DATA")
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if err != nil {
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return nil, err
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}
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return &dataCloser{c, c.Text.DotWriter()}, nil
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}
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// SendMail connects to the server at addr, switches to TLS if possible,
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// authenticates with mechanism a if possible, and then sends an email from
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// address from, to addresses to, with message msg.
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func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
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c, err := Dial(addr)
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if err != nil {
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return err
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}
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if ok, _ := c.Extension("STARTTLS"); ok {
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if err = c.StartTLS(nil); err != nil {
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return err
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}
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}
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if a != nil && c.ext != nil {
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if _, ok := c.ext["AUTH"]; ok {
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if err = c.Auth(a); err != nil {
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return err
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}
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}
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}
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if err = c.Mail(from); err != nil {
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return err
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}
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for _, addr := range to {
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if err = c.Rcpt(addr); err != nil {
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return err
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}
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}
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w, err := c.Data()
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if err != nil {
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return err
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}
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_, err = w.Write(msg)
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if err != nil {
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return err
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}
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err = w.Close()
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if err != nil {
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return err
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}
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return c.Quit()
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}
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// Extension reports whether an extension is support by the server.
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// The extension name is case-insensitive. If the extension is supported,
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// Extension also returns a string that contains any parameters the
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// server specifies for the extension.
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func (c *Client) Extension(ext string) (bool, string) {
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if c.ext == nil {
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return false, ""
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}
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ext = strings.ToUpper(ext)
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param, ok := c.ext[ext]
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return ok, param
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}
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// Reset sends the RSET command to the server, aborting the current mail
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// transaction.
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func (c *Client) Reset() error {
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_, _, err := c.cmd(250, "RSET")
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return err
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}
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// Quit sends the QUIT command and closes the connection to the server.
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func (c *Client) Quit() error {
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_, _, err := c.cmd(221, "QUIT")
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if err != nil {
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return err
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}
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return c.Text.Close()
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}
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