Lotus Notes 7.0.2 doesn’t receive invitations from Outlook2007

I have a problem with Outlook 2007 that I am yet to figure out.
The problem is that whenever I send updates or invitations to our employees some of them don’t receive them.
This happens only to those using Lotus Notes 7.0.2.
How will I ensure that all of them get all our outlook invitations?
I am now looking for a solution that will end this problem.
I hope you will help.
