diff --git a/docs/docs/en/guide/start/docker.md b/docs/docs/en/guide/start/docker.md
index 9e143f0bbc..5265fa3ce5 100644
--- a/docs/docs/en/guide/start/docker.md
+++ b/docs/docs/en/guide/start/docker.md
@@ -977,7 +977,7 @@ Configure the mail service port for `alert-server`, default value `empty`.
 
 Configure the mail sender for `alert-server`, default value `empty`.
 
-**`MAIL_USER=`**
+**`MAIL_USER`**
 
 Configure the user name of the mail service for `alert-server`, default value `empty`.