diff --git a/sendmail.go b/sendmail.go
index 7595eec..730332f 100644
--- a/sendmail.go
+++ b/sendmail.go
@@ -91,6 +91,7 @@ func (m *SendMailRequest) Execute() error {
 	if err != nil {
 		return fmt.Errorf("failed initiating smtp connection (%s)", err)
 	}
+	defer conn.Close()
 
 	smtpClient, err := smtp.NewClient(conn, smtpServerHost)
 	if err != nil {