package send import ( "crypto/tls" "fmt" "io" "net/url" "strings" "github.com/emersion/go-message/mail" "github.com/emersion/go-smtp" "github.com/pkg/errors" ) func connectSmtp(starttls bool, host string, domain string) (*smtp.Client, error) { serverName := host if !strings.ContainsRune(host, ':') { host += ":587" // Default to submission port } else { serverName = host[:strings.IndexRune(host, ':')] } var conn *smtp.Client var err error if starttls { conn, err = smtp.DialStartTLS(host, &tls.Config{ServerName: serverName}) } else { conn, err = smtp.Dial(host) } if err != nil { return nil, errors.Wrap(err, "smtp.Dial") } if domain != "" { err := conn.Hello(domain) if err != nil { conn.Close() return nil, errors.Wrap(err, "Hello") } } return conn, nil } func connectSmtps(host string) (*smtp.Client, error) { serverName := host if !strings.ContainsRune(host, ':') { host += ":465" // Default to smtps port } else { serverName = host[:strings.IndexRune(host, ':')] } conn, err := smtp.DialTLS(host, &tls.Config{ ServerName: serverName, }) if err != nil { return nil, errors.Wrap(err, "smtp.DialTLS") } return conn, nil } type smtpSender struct { conn *smtp.Client w io.WriteCloser } func (s *smtpSender) Write(p []byte) (int, error) { return s.w.Write(p) } func (s *smtpSender) Close() error { we := s.w.Close() ce := s.conn.Close() if we != nil { return we } return ce } func newSmtpSender( protocol string, auth string, uri *url.URL, domain string, from *mail.Address, rcpts []*mail.Address, ) (io.WriteCloser, error) { var err error var conn *smtp.Client switch protocol { case "smtp": conn, err = connectSmtp(true, uri.Host, domain) case "smtp+insecure": conn, err = connectSmtp(false, uri.Host, domain) case "smtps": conn, err = connectSmtps(uri.Host) default: return nil, fmt.Errorf("not a smtp protocol %s", protocol) } if err != nil { return nil, errors.Wrap(err, "Connection failed") } saslclient, err := newSaslClient(auth, uri) if err != nil { conn.Close() return nil, err } if saslclient != nil { if err := conn.Auth(saslclient); err != nil { conn.Close() return nil, errors.Wrap(err, "conn.Auth") } } s := &smtpSender{ conn: conn, } if err := s.conn.Mail(from.Address, nil); err != nil { conn.Close() return nil, errors.Wrap(err, "conn.Mail") } for _, rcpt := range rcpts { if err := s.conn.Rcpt(rcpt.Address, nil); err != nil { conn.Close() return nil, errors.Wrap(err, "conn.Rcpt") } } s.w, err = s.conn.Data() if err != nil { conn.Close() return nil, errors.Wrap(err, "conn.Data") } return s.w, nil }