diff --git a/client.go b/client.go
index aae425c..f0e604f 100644
--- a/client.go
+++ b/client.go
@@ -550,6 +550,46 @@ func (c *Client) Data() (io.WriteCloser, error) {
 	return &dataCloser{c, c.Text.DotWriter(), nil}, nil
 }
 
+// SendMail will use an existing connection to send an email from
+// address from, to addresses to, with message r.
+//
+// This function does not start TLS, nor does it perform authentication. Use
+// StartTLS and Auth before-hand if desirable.
+//
+// The addresses in the to parameter are the SMTP RCPT addresses.
+//
+// The r parameter should be an RFC 822-style email with headers
+// first, a blank line, and then the message body. The lines of r
+// should be CRLF terminated. The r headers should usually include
+// fields such as "From", "To", "Subject", and "Cc".  Sending "Bcc"
+// messages is accomplished by including an email address in the to
+// parameter but not including it in the r headers.
+func (c *Client) SendMail(from string, to []string, r io.Reader) error {
+	var err error
+
+	if err = c.Mail(from, nil); err != nil {
+		return err
+	}
+	for _, addr := range to {
+		if err = c.Rcpt(addr, nil); err != nil {
+			return err
+		}
+	}
+	w, err := c.Data()
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(w, r)
+	if err != nil {
+		return err
+	}
+	err = w.Close()
+	if err != nil {
+		return err
+	}
+	return c.Quit()
+}
+
 // LMTPData is the LMTP-specific version of the Data method. It accepts a callback
 // that will be called for each status response received from the server.
 //
@@ -624,27 +664,7 @@ func SendMail(addr string, a sasl.Client, from string, to []string, r io.Reader)
 			return err
 		}
 	}
-	if err = c.Mail(from, nil); err != nil {
-		return err
-	}
-	for _, addr := range to {
-		if err = c.Rcpt(addr, nil); err != nil {
-			return err
-		}
-	}
-	w, err := c.Data()
-	if err != nil {
-		return err
-	}
-	_, err = io.Copy(w, r)
-	if err != nil {
-		return err
-	}
-	err = w.Close()
-	if err != nil {
-		return err
-	}
-	return c.Quit()
+	return c.SendMail(from, to, r)
 }
 
 // Extension reports whether an extension is support by the server.
diff --git a/conn.go b/conn.go
index 6276683..862c0f9 100644
--- a/conn.go
+++ b/conn.go
@@ -787,6 +787,7 @@ func (c *Conn) handleStartTLS() {
 		session.Logout()
 		c.SetSession(nil)
 	}
+	c.helo = ""
 	c.didAuth = false
 	c.reset()
 }
diff --git a/go.mod b/go.mod
index ae2641e..12b5518 100644
--- a/go.mod
+++ b/go.mod
@@ -1,14 +1,14 @@
 module github.com/linanh/go-smtp
 
+go 1.15
+
 require (
 	github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21
 	github.com/gomodule/redigo v2.0.0+incompatible // indirect
-	github.com/google/uuid v1.2.0
-	github.com/throttled/throttled/v2 v2.9.0
+	github.com/google/uuid v1.3.0
+	github.com/throttled/throttled/v2 v2.9.1
 	github.com/txthinking/socks5 v0.0.0-20210716140126-fa1f52a8f2da
 	go.uber.org/atomic v1.9.0 // indirect
 	go.uber.org/multierr v1.7.0 // indirect
 	go.uber.org/zap v1.19.0
 )
-
-go 1.15
diff --git a/go.sum b/go.sum
index f1df00b..dda7ab1 100644
--- a/go.sum
+++ b/go.sum
@@ -21,8 +21,8 @@ github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMyw
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/uuid v1.2.0 h1:qJYtXnJRWmpe7m/3XlyhrsLrEURqHRM2kxzoxXqyUDs=
-github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/golang-lru v0.5.4 h1:YDjusn29QI/Das2iO9M0BHnIbxPeyuCHsjMW+lJfyTc=
 github.com/hashicorp/golang-lru v0.5.4/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
@@ -46,8 +46,8 @@ github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81P
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/throttled/throttled/v2 v2.9.0 h1:DOkCb1el7NYzRoPb1pyeHVghsUoonVWEjmo34vrcp/8=
-github.com/throttled/throttled/v2 v2.9.0/go.mod h1:0JHxhGAidPyqbgD4HF8Y1sNFfG0ffVXK6C8EpkNdLEM=
+github.com/throttled/throttled/v2 v2.9.1 h1:Es7fBRL04IUOvs4RwbieshgyccyztfaAjzQdKbrpqyo=
+github.com/throttled/throttled/v2 v2.9.1/go.mod h1:SxVlv4wUgeS/hWOSMDeb9Ez+stPqP7tWY5wI5BUiGqs=
 github.com/txthinking/runnergroup v0.0.0-20210608031112-152c7c4432bf h1:7PflaKRtU4np/epFxRXlFhlzLXZzKFrH5/I4so5Ove0=
 github.com/txthinking/runnergroup v0.0.0-20210608031112-152c7c4432bf/go.mod h1:CLUSJbazqETbaR+i0YAhXBICV9TrKH93pziccMhmhpM=
 github.com/txthinking/socks5 v0.0.0-20210716140126-fa1f52a8f2da h1:7x8pJcBTdKTBpQbRjZZc9o6CDquXBbvm9UIrR6ZSRJ4=
@@ -77,7 +77,7 @@ golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20191010194322-b09406accb47/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20191108193012-7d206e10da11 h1:Yq9t9jnGoR+dBuitxdo9l6Q7xh/zOyNnYUtDKaQ3x0E=
diff --git a/server.go b/server.go
index 8afa5c1..c154b70 100644
--- a/server.go
+++ b/server.go
@@ -113,6 +113,8 @@ func (s *Server) Serve(l net.Listener) error {
 	s.listeners = append(s.listeners, l)
 	s.locker.Unlock()
 
+	var tempDelay time.Duration // how long to sleep on accept failure
+
 	for {
 		c, err := l.Accept()
 		if err != nil {
@@ -121,11 +123,29 @@ func (s *Server) Serve(l net.Listener) error {
 				// we called Close()
 				return nil
 			default:
-				return err
 			}
+			if ne, ok := err.(net.Error); ok && ne.Temporary() {
+				if tempDelay == 0 {
+					tempDelay = 5 * time.Millisecond
+				} else {
+					tempDelay *= 2
+				}
+				if max := 1 * time.Second; tempDelay > max {
+					tempDelay = max
+				}
+				s.Logger.Infof("smtp/server accept error: %s; retrying in %s", err, tempDelay)
+				time.Sleep(tempDelay)
+				continue
+			}
+			return err
 		}
 
-		go s.handleConn(newConn(c, s))
+		go func() {
+			err := s.handleConn(newConn(c, s))
+			if err != nil {
+				s.Logger.Infof("smtp/server error: %s", err)
+			}
+		}()
 	}
 }
 
@@ -161,6 +181,19 @@ func (s *Server) handleConn(c *Conn) error {
 		s.locker.Unlock()
 	}()
 
+	if tlsConn, ok := c.conn.(*tls.Conn); ok {
+		if d := s.ReadTimeout; d != 0 {
+			c.conn.SetReadDeadline(time.Now().Add(d))
+		}
+		if d := s.WriteTimeout; d != 0 {
+			c.conn.SetWriteDeadline(time.Now().Add(d))
+		}
+		if err := tlsConn.Handshake(); err != nil {
+			s.Logger.Infof("smtp/server sid=%s reject: TLS handshake error for %s, %s", c.sid, addr, err.Error())
+			return err
+		}
+	}
+
 	c.greet()
 
 	for {