MX for backup link?

[Gene Frederick F. Boniel]

ISP B
     +
     |
     |          domain.com
     |
     |
 (s0=y.y.y.x)
   wingate                            linux
 (e0=x.x.x.1)                      (e0=x.x.x.2)
    +                                   +
    |                                   |
    |                                   |
    |            x.x.x.n                |
    +----+------+------+-------+--------+--------+router+----- ISP A
         W1     W2     W3     W4

  1. linux machine is the primary domain server for domain.com
  2. connection to ISP B is dedicated dial-up
  3. connection to ISP A is via leased line and this is the default route.
  4. wingate has SMTP Mapping service.

  linux.domain.com.     IN      A       x.x.x.2
  wingate.domain.com.   IN      A       y.y.y.x
  domain.com.           IN      MX      10 linux.domain.com.
  domain.com.           IN      MX      20 wingate.domain.com.

     if i set the 2 machines as mail exchangers for domain.com,  would 
incoming emails pass through the wingate machine if my link to ISP A goes down 
?
can MX do that ?


thanks in advance.

DeSpErAd0