Outlook meeting request undeliverable

Have a strange situation, but most Outlook “q”s are.
When my boss sends out a meeting request he gets a undeliverable for 2 recipients that aren’t with the company anymore and do not have existing e-mail accounts.

I looked throughout his Outlook(2002) settings but couldn’t find anything with their names.

It appears to not matter who the request is sent to, it always bounces back undeliverable to these 2 former employees.

Any ideas?

Doc