2017-07-31 10:19:16 -05:00
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# How to mark a mail domain as backup MX
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[TOC]
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This tutorial describes how to mark a mail domain as a backup MX.
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## How backup MX works in brief
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When smtp service on primary MX server is down, emails will be delivered to
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backup MX server. When backup MX server detects smtp service on primary MX is
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back online, it will relay received emails to primary MX.
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## Make sure you have correct DNS records for the mail domain
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To let other mail servers know your server is the backup MX server of this
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mail domain, you must add your mail server info in its MX type DNS record.
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For example, main mail server of your mail domain `example.com` is
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`mx01.example.com`, to set your iRedMail server `mx02.example.com` as backup
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MX of `example.com`, you need to add `mx02.example.com` as your lower priority
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2019-06-06 02:36:43 -05:00
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mail server in MX type DNS record.
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2017-07-31 10:19:16 -05:00
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```
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example.com. 3600 IN MX 5 mx01.example.com
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example.com. 3600 IN MX 10 mx02.example.com
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```
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Server `mx01.example.com` has priority number `5`, and `mx02.example.com` has
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priority number `10`. For mail service, the lowest number has highest priority.
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so with above example, server `mx01.example.com` is the primary MX, and
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`mx02.example.com` is a backup MX.
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When mail service on `mx01.example.com` is down, other mail services will
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connect to `mx02.example.com`.
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## Mark domain as backup MX with iRedAdmin-Pro
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It's easy to manage domain profile With iRedAdmin-Pro, including backup MX setting.
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Go to domain profile page, click tab `Backup MX`:
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2017-11-16 21:48:44 -06:00
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![](./images/iredadmin/domain_profile_backupmx.png){: width=1000px }
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2017-07-31 10:19:16 -05:00
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## Mark domain as backup MX with command line tools
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### For SQL backends
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!!! note "Primary server address"
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You should set the IP address of primary MX as relay server to avoid mail
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loop.
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SQL commands (we use MySQL for example):
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```
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USE vmail;
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UPDATE domain SET transport='relay:[45.56.127.226]:25',backupmx=1 WHERE domain='example.com';
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```
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In above example, we mark domain `example.com` as a backup MX, and use IP
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address `45.56.127.226` as primary MX server, you should replace it by the real
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IP address.
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### For LDAP backends
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In domain object, please add LDAP attribute/value pair like below:
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```
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domainBackupMX: yes
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mtaTransport: relay:[45.56.127.226]:25
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```
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2017-07-31 10:22:47 -05:00
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## See also
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* [Backup MX (wikipedia)](https://en.wikipedia.org/wiki/MX_record#The_backup_MX)
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