To open a meeting request in the Mail for Exchange mailbox, select the meeting request.
To accept a meeting request select Options > Response > Accept. The meeting will be added to your device calendar if calendar entries are being synchronised.
To tentatively accept a meeting request select Options > Response > Tentative. The meeting will be added to your device calendar if calendar entries are being synchronised.
To reject a meeting request select Options > Response > Decline. The meeting will not appear in your device calendar.