MX Record Problem?

[Doug Snowden]

I have an older IBM machine that has been our
mail machine for some time now. It is running
AIX 3.2.5 and sendmail.  I also have a linux box running linux 5.0 and
sendmail.  In our dns file (AIX 3.2.5 machine)
I have the IBM machine as MX 20 and the linux
box as MX 10.  Eventually I want to remove the
IBM machine and have the linux box do mail alone.
As it stands now, with both IBM and linux running
I get some mail from the linux box and some from the IBM box.  It is not

random, because if I look
at messages from certain sites, they always go to
a particular machine at all times.  I'm pretty
confused here.  Don't know if I have something
configured wrong or what. Maybe some external mail
packages don't know or like MX records?

Thanks, Doug