diff --git a/en_US/howto/backupmx.md b/en_US/howto/backupmx.md
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+# How to mark a mail domain as backup MX
+
+[TOC]
+
+This tutorial describes how to mark a mail domain as a backup MX.
+
+## How backup MX works in brief
+
+When smtp service on primary MX server is down, emails will be delivered to
+backup MX server. When backup MX server detects smtp service on primary MX is
+back online, it will relay received emails to primary MX.
+
+## Make sure you have correct DNS records for the mail domain
+
+To let other mail servers know your server is the backup MX server of this
+mail domain, you must add your mail server info in its MX type DNS record.
+
+For example, main mail server of your mail domain `example.com` is
+`mx01.example.com`, to set your iRedMail server `mx02.example.com` as backup
+MX of `example.com`, you need to add `mx02.example.com` as your lower priority
+mail server in MX type DNS record.
+
+```
+example.com. 3600 IN MX 5 mx01.example.com
+example.com. 3600 IN MX 10 mx02.example.com
+```
+
+Server `mx01.example.com` has priority number `5`, and `mx02.example.com` has
+priority number `10`. For mail service, the lowest number has highest priority.
+so with above example, server `mx01.example.com` is the primary MX, and
+`mx02.example.com` is a backup MX.
+
+When mail service on `mx01.example.com` is down, other mail services will
+connect to `mx02.example.com`.
+
+## Mark domain as backup MX with iRedAdmin-Pro
+
+It's easy to manage domain profile With iRedAdmin-Pro, including backup MX setting.
+Go to domain profile page, click tab `Backup MX`:
+
+{: width=1000px }
+
+## Mark domain as backup MX with command line tools
+
+### For SQL backends
+
+!!! note "Primary server address"
+
+ You should set the IP address of primary MX as relay server to avoid mail
+ loop.
+
+SQL commands (we use MySQL for example):
+
+```
+USE vmail;
+UPDATE domain SET transport='relay:[45.56.127.226]:25',backupmx=1 WHERE domain='example.com';
+```
+
+In above example, we mark domain `example.com` as a backup MX, and use IP
+address `45.56.127.226` as primary MX server, you should replace it by the real
+IP address.
+
+
+### For LDAP backends
+
+In domain object, please add LDAP attribute/value pair like below:
+
+```
+domainBackupMX: yes
+mtaTransport: relay:[45.56.127.226]:25
+```
diff --git a/html/backupmx.html b/html/backupmx.html
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+
+
+
+
+ How to mark a mail domain as backup MX
+
+
+
+
+
This tutorial describes how to mark a mail domain as a backup MX.
+
How backup MX works in brief
+
When smtp service on primary MX server is down, emails will be delivered to
+backup MX server. When backup MX server detects smtp service on primary MX is
+back online, it will relay received emails to primary MX.
+
Make sure you have correct DNS records for the mail domain
+
To let other mail servers know your server is the backup MX server of this
+mail domain, you must add your mail server info in its MX type DNS record.
+
For example, main mail server of your mail domain example.com is
+mx01.example.com, to set your iRedMail server mx02.example.com as backup
+MX of example.com, you need to add mx02.example.com as your lower priority
+mail server in MX type DNS record.
+
example.com. 3600 IN MX 5 mx01.example.com
+example.com. 3600 IN MX 10 mx02.example.com
+
+
+
Server mx01.example.com has priority number 5, and mx02.example.com has
+priority number 10. For mail service, the lowest number has highest priority.
+so with above example, server mx01.example.com is the primary MX, and
+mx02.example.com is a backup MX.
+
When mail service on mx01.example.com is down, other mail services will
+connect to mx02.example.com.
+
Mark domain as backup MX with iRedAdmin-Pro
+
It's easy to manage domain profile With iRedAdmin-Pro, including backup MX setting.
+Go to domain profile page, click tab Backup MX:
+
+
Mark domain as backup MX with command line tools
+
For SQL backends
+
+
Primary server address
+
You should set the IP address of primary MX as relay server to avoid mail
+loop.
+
+
SQL commands (we use MySQL for example):
+
USE vmail;
+UPDATE domain SET transport='relay:[45.56.127.226]:25',backupmx=1 WHERE domain='example.com';
+
+
+
In above example, we mark domain example.com as a backup MX, and use IP
+address 45.56.127.226 as primary MX server, you should replace it by the real
+IP address.
+
For LDAP backends
+
In domain object, please add LDAP attribute/value pair like below:
+
+
\ No newline at end of file
diff --git a/html/index.html b/html/index.html
index a6e9d395..4fddc940 100644
--- a/html/index.html
+++ b/html/index.html
@@ -104,6 +104,7 @@
+ iRedMail
+
+ // Document Index