diff --git a/smtp/smtp.go b/smtp/smtp.go
index 4841ec8..943ca9d 100644
--- a/smtp/smtp.go
+++ b/smtp/smtp.go
@@ -432,8 +432,6 @@ func (c *Client) Data() (io.WriteCloser, error) {
 	return datacloser, nil
 }
 
-var testHookStartTLS func(*tls.Config) // nil, except for tests
-
 // SendMail connects to the server at addr, switches to TLS if
 // possible, authenticates with the optional mechanism a if possible,
 // and then sends an email from address from, to addresses to, with
@@ -475,9 +473,6 @@ func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
 	}
 	if ok, _ := c.Extension("STARTTLS"); ok {
 		config := &tls.Config{ServerName: c.serverName}
-		if testHookStartTLS != nil {
-			testHookStartTLS(config)
-		}
 		if err = c.StartTLS(config); err != nil {
 			return err
 		}