"yum install postfix" tries to install netqmail instead

Hello,

I have a RHEL 5 system which is subscribed to the Red Hat Network for system
updates and also attached to a local yum repository. In this local repository
I have a custom-rolled rpm for netqmail, which we use on other machines in our
site.

When I attempt to install postfix on the system, it doesn't exactly perform as
expected:

> [root@somehost ~]# yum install postfix
> Loading "security" plugin
> Loading "rhnplugin" plugin
> somehost.local-instal 100% |=========================| 1.1 kB    00:00     
> rhel-x86_64-client-w 100% |=========================| 1.2 kB    00:00     
> rhel-x86_64-client-s 100% |=========================| 1.2 kB    00:00     
> somehost-install         100% |=========================| 1.1 kB    00:00     
> rhel-x86_64-client-5 100% |=========================| 1.2 kB    00:00     
> rhn-tools-rhel-x86_6 100% |=========================| 1.2 kB    00:00          
> Excluding Packages in global exclude list
> Finished
> Setting up Install Process
> Parsing package install arguments
> Resolving Dependencies
> --> Running transaction check
> ---> Package netqmail.x86_64 0:1.05-SEC.1_FC6 set to be updated
> --> Processing Dependency: ucspi-tcp >= 0.88 for package: netqmail
> --> Processing Dependency: daemontools >= 0.76 for package: netqmail
> --> Running transaction check
> ---> Package daemontools.x86_64 0:0.76-SEC.25_FC6 set to be updated
> ---> Package ucspi-tcp.x86_64 0:0.88-SEC.16_FC6 set to be updated
> --> Finished Dependency Resolution
>
> Dependencies Resolved
>
> =============================================================================
>  Package                 Arch       Version          Repository        Size
> =============================================================================
> Installing:
>  netqmail                x86_64     1.05-SEC.1_FC6   somehost-install  405 k
> Installing for dependencies:
>  daemontools             x86_64     0.76-SEC.25_FC6  somehost-install   63 k
>  ucspi-tcp               x86_64     0.88-SEC.16_FC6  somehost-install   89 k
>
> Transaction Summary
> =============================================================================
> Install      3 Package(s)         
> Update       0 Package(s)         
> Remove       0 Package(s)         
>
> Total download size: 558 k
> Is this ok [y/N]:

As you can see, it tries to install netqmail from the local repos instead.

I've done a "yum clean all" and even completely wiped out /var/cache/yum, but
the behavior is consistent unless I take the drastic measure of completely
removing netqmail from my local repositories. Then yum finds and installs
postfix from the Red Hat Network repos.

All I can figure is that yum is preferentially looking for a capability match
here (netqmail being an alternative mail package to postfix) rather than
looking for an exact package name match. If this is the case, is there any way
to disable this?

Thanks for your help!
Quellyn Snead