diff --git a/en_US/installation/0-install.iredmail.with.remote.mysql.server.md b/en_US/installation/0-install.iredmail.with.remote.mysql.server.md
index ecb400b0..418458f4 100644
--- a/en_US/installation/0-install.iredmail.with.remote.mysql.server.md
+++ b/en_US/installation/0-install.iredmail.with.remote.mysql.server.md
@@ -98,6 +98,9 @@ mysql> DROP USER 'vmailadmin'@'192.168.1.200';
 Please follow iRedMail installation guide strictly, but start iRedMail
 installer with below command instead of the original one (`bash iRedMail.sh`):
 
+> WARNING: the variable names (`MYSQL_SERVER`, `MYSQL_ROOT_USER`,
+> `MYSQL_GRANT_HOST`) are __CASE SENSITIVE__.
+
 ```
 # MYSQL_SERVER='192.168.1.100' MYSQL_ROOT_USER='admin_iredmail' MYSQL_GRANT_HOST='192.168.1.200' bash iRedMail.sh
 ```
diff --git a/html/install.iredmail.with.remote.mysql.server.html b/html/install.iredmail.with.remote.mysql.server.html
index f3bc6a50..59f9d793 100644
--- a/html/install.iredmail.with.remote.mysql.server.html
+++ b/html/install.iredmail.with.remote.mysql.server.html
@@ -110,6 +110,10 @@ mysql> DROP USER 'vmailadmin'@'192.168.1.200';
 <h2 id="install-iredmail">Install iRedMail</h2>
 <p>Please follow iRedMail installation guide strictly, but start iRedMail
 installer with below command instead of the original one (<code>bash iRedMail.sh</code>):</p>
+<blockquote>
+<p>WARNING: the variable names (<code>MYSQL_SERVER</code>, <code>MYSQL_ROOT_USER</code>,
+<code>MYSQL_GRANT_HOST</code>) are <strong>CASE SENSITIVE</strong>.</p>
+</blockquote>
 <pre><code># MYSQL_SERVER='192.168.1.100' MYSQL_ROOT_USER='admin_iredmail' MYSQL_GRANT_HOST='192.168.1.200' bash iRedMail.sh
 </code></pre>