MX choosing

[Phil Mayers]

On 07/22/2011 09:50 AM, Feng He wrote:
> Given the MX hosts for sympatico.ca domain:
>
> $ dig sympatico.ca mx +short
> 5 mxmta.sympatico.ca.
>
> $ dig mxmta.sympatico.ca +short
> 67.69.240.17
> 67.69.240.24
> 67.69.240.22
> 67.69.240.23
> 67.69.240.21
> 67.69.240.20
> 67.69.240.19
> 67.69.240.18
>
>
> when the peer MTA fail to talk to one of these hosts,will it try the
> next one? or it just give up?

It should try the next one, but there is a lot of crappy MTA software 
out there.

See section 5 of RFC 5321, or earlier RFC 2821, or section 5 of RFC 1123 
and earlier RFCs 821 and 974, for details.