Yum looking for wrong file

[Harry Putnam]

I keep a mirror of the main rawhide repo, or at least it is supposed
to be a mirror.  But apparently something is different between the
real repo and my mirror.  I'd like to find out what.

If I run yum against my repo to update mozilla-mail with

   yum --obsoletes update mozilla-mail

It returns with an error that it cannot find filename:
   Fedora/RPMS/mozilla-mail-1.7.3-13.i386.rpm

Well that is the wrong file name.  The 13 should be a 17.  I just
finished my mirroring program and looking in my mirror I see 

  mozilla-mail-1.7.3-17.i386.rpm (The correct file)

Where does yum get the filenames it looks for?  I'm guessing some file
on the real repo is not getting downloaded to my mirror and therefore
some incorrect stuff is happening.

Can someone tell me where the filename is comming from?

PS- If I run yum the same way but aimed at the real repo it finds the
correct file.