diff --git a/outputs/customsmtp/smtp.go b/outputs/customsmtp/smtp.go
index 7b1542ad..2fec7fcc 100644
--- a/outputs/customsmtp/smtp.go
+++ b/outputs/customsmtp/smtp.go
@@ -194,8 +194,8 @@ func (c *Client) Auth(a Auth) error {
 	resp64 := make([]byte, encoding.EncodedLen(len(resp)))
 	encoding.Encode(resp64, resp)
 	respEncoded := string(resp64)
-	authString := fmt.Sprintf("AUTH %s %s", mech, respEncoded)
-	code, msg64, err := c.cmd(0, strings.TrimSpace(authString))
+	authString := strings.TrimSpace(fmt.Sprintf("AUTH %s %s", mech, respEncoded))
+	code, msg64, err := c.cmd(0, authString)
 	for err == nil {
 		var msg []byte
 		switch code {