Olá

Pessoal estou com dúvidas, qual será á prioridade que estou criando backup de MX para não perder emails

 

MX 0 Dominio.xxxxx
MX 10 DOMINIOXXX.COM
MX 20 DOMINIOXXX.NET

Eu apontando um MX para cada servidor não terá o risco de perder e-mails correto ? 
 

Eu estava para falar disso aqui lá no blog

Citar

 

The MX numbers describe in which order the email servers are contacted when trying to deliver an email message. The server with the lowest MX number has the highest priority. Email sent to your domain will therefore be sent to the server with the lowest MX value. If the server with the highest priority (lowest MX value) becomes unavailable for any reason the next highest mail server will be used. If that one is also not available the next highest and so on. If two mail servers have the same MX priority one will be picked randomly by the sending server.

It’s a relative number, so you don’t need an MX priority of 1 for your primary mail server but only have to make sure that it has the lowest MX value

 

Fonte: http://www.sysadminworld.com/2011/what-is-the-difference-between-mx-priority-1234-and-10203040/

Resumindo: Vc pode usar as prioridades 1, 2, 3 ou 10, 20, 30, desde que a prioridade mais baixa seja a principal. No caso dela falhar, o email vai pra prioridade seguinte na lista (2 ou 20, no exemplo). Mas lembre de configurar estes outros domínios e servidores para receber os emails.