If you package in 2000 then 2003 will be able to read it

What you want is Late Binding.

Rather than set a reference to Outlook (which is linked to a specific version),
you would do something like this ...

Dim objOutlook As Object
Set objOutlook = CreateObject("Outlook.Application")

The problem is that you don't get intellisense when you do this, so I usually
write my code with bound objects, using a specific reference, and then unbind
them before delivery ... or whenever I'm done working with the objects.

Late binding. This allows you to make use of external libraries without
setitng a reference to them and (for the most part) makes the code version
independent.

I have no interest in changing or criticizing anyone's practice of
automating Outlook in order to send e-mails.

I used to do this myself. I wrote my first code to do so about eight
years ago. Not so surprisingly there was a discussion then about early
and late binding.

I note there are many posts to CDMA outlining problems with automating
Outlook. I had problems myself, notably when system administrators
enetered fake addresses into system address books in order to confuse
the Melissa virus. They were successfull and they were also successful
in disabling an address search in my application. As they didn't tell
anyone, let alone me, of their covert activity, I was at a loss to
explain why the application worked one day, but not the next. [My first
rule of Access is: It's IT ('s fault).]

For beginners or non-previous-email senders who lurk I would like to
point out that beginning with Windows 2000, Microsoft has provided us
with CDO. CDO is implemented through CDOSys.Dll. CDO sends mail
quietly, simply, quickly, without warning messages and without fuss. I
use CDO now, I don't use Outlook.