Les,
You don't mention that accessing the file is a problem, so I doubt that
the file is corrupted. However, it could be if you take a look at
http://project.mvps.org/faqs.htm#Handling_project_file_corruption_and/or_bloat
you can see if any of the ideas there result in reducing the file size.
6000 tasks and 12 mb is a large file. It's probable that 12 mb is the
file size it needs to be.
My preference for such large projects is to always break it into a
number of subproject files and use a master file that pulls it all
together. This approach reduces individual file sizes although the sum
may be as big as the starting file size. What is gained is faster
loading/saving time, ability to get multiple people working on
individual files simultaneously. You also then could send the files
individually.
To send the 12 mb file where you have such mail server restrictions,
there are some file splitter programs available. PC Magazine gave one
away years ago that I used to use with success. I also notice that
WinZip has the ability to split files, but I have not used it.
The other idea is to find a commonly available file share, SharePoint
server, or even an FTP server where you can exchange the file. All that
dependant, of course, of such availability to you.
--rms
www.rmschneider.com