Multiple email addresses for one contact

[Top Spin]

We are starting to use email more and more for business clients.
Several of them are asking that we send copies of every message to two
different email addresses (usually home and work).

Is there a recommended way to set the client up so that sending an
email to that contact will generate copies to two email addesses
automatically?

I do not want to try and remember which clients want duplicate emails.

I do not want to set up a distribution list for those clients because
I would then have to remember which clients to use the distribution
list for.

I tried putting 2 email addresses in the email box separated by
semi-colons, but outlook complained about that.

I also tried setting up a second contact for that client and then
creating a distribution list for that client with both addresses and
then putting the distribution list in the email box, but that was also
rejected.

I would like something simple like just putting 2 addresses in the
email box.

Thanks