Your mailbox can be configured to process external meeting requests and meeting responses. You can enable this feature by using OWA, or an Exchange administrator can enable it for you by using the Exchange Management Shell.
Use OWA to enable the processing of external meeting responses
Outlook Web Access- Log on to OWA, and then click Options.
- Click Calendar Options, and then click to select the Automatically process requests and responses from external senders check box under Automatic Calendar Processing.
- Click Save to apply the changes.
Outlook Web App- Log on to OWA, click Options, and then click See All Options.
- Click Settings, and then click Calendar.
- Under Automatic Processing, click to enable the Automatically process requests and responses from external senders check box.
- Click Save to apply the changes.
Use the Exchange Management Shell to enable the processing of external meeting responses
The Exchange Server administrator must start the Exchange Management Shell on the Exchange mailbox server and then run the following command in the Exchange Management Shell:
Set-mailboxcalendarsettings username -ProcessExternalMeetingMessages $true
where username is the affected user's alias.