[exim] How to Always Use The Same MX ?

Hello,

I hope experts here could give some help on this.
I have this question about exim config, it looks pretty direct, but I really
couldn't figure it out.

If I want to send an email to a remote host (abc.com), and this remote host
has 3 MX, namely:-

mx1.abc.com
mx2.abc.com
mx3.abc.com

How do I ask exim to always connect and talk to mx3.abc.com and ignore the
priorities ?

And how to do this setup so that it only affects anyemail@??? ?

All other remote host, yahoo.com, hotmail.com, should be using default
settings and choose mx according to priority.

Please help, this has taken me days and I still couldn't figure it out.

Thanks

Alson