We are going through an AD migration of 3 AD's to 1 new one.. We have a sharepoint foundation 2013 server on one of the old domains which still needs to be used (used as a room booking calendar).
Users are still able to use it with their migrated usernames on the new domain and make room bookings etc but there is a field used for a "booking notification" (which sends the person booking a confirmation and calendar appointment) but this field is not picking up any users (unsurprising since they are in a different domain now)
I'm in no way expert in sharepoint, I have admin privileges but no idea how to go about fixing the people lookup.
Where do I start? Two way trusts exist between each domain to new one. SharePoint server is still on old domain.. didn't want to migrate it over to new domain until found out correct methodology and it's pretty much not broken apart from this one problem so didn't want to make the problem worse.