I have a user who regularly sets up meeting requests and it has just come to light that when attendees accept the request, 3 other members of staff always get the acceptance as well as the originator. Is there any reason why this should happen, the only thing I can find where all 4 users are connected is that they are all in a distribution group, which in ADU&C was set as a Domain Local list when all our other distribution lists are set as Global. Apparently this has been going on for quite some time!! I can't for the life of me figure out whay this happens on meeting acceptances and nothing else!

does the user sending the meeting request have delegates defined in outlook?

I have a feeling they do have delegates setup but no one else in the organisation who have delegates set up seem to have this problem. I have a feweling they may have a rule set up to forward meetign aceptances. I'll have to check this out

Delegate access to the calender was part of the answer. There was a check box for delegates to receive meeting notifications. Removed that tick!