{{tag>tutorial mail}}

====== Configure postfix as a backup for Exchange ======

===== Problem =====
  * I want to use postfix on a virtual server as a backup in case my Exchange is down. Postfix should accept every mail and deliver it to the Exchange server instantly or wait until the Exchange server is available.

===== Requirements =====
  * Existing postfix installation
  * Existing Exchange installation

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===== Step 1 =====
  * Login to your virtual server via ssh.

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===== Step 2 =====
  * Create and open the file ''%%/etc/postfix/transport%%''
  * Insert ''%%domain.com smtp:exchangehost.name%%'' for every domain you want to relay on its own line.
  * Run ''%%postmap /etc/postfix/transport%%''

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===== Step 3 =====
  * Edit ''%%/etc/postfix/main.cf%%''
  * Insert ''%%relay_domains = domain.com%%''. If you want multiple domains, separate them with a space.
  * Insert ''%%transport_maps = hash:/etc/postfix/transport%%''
  * Run ''%%/etc/init.d/postfix reload%%''