Hope everyone is well. I needed some advice please. My internal domain is mycompany.local and the external domain name is mycompany.co.za. On the on-premise DNS servers I noticed we had static A records configured namely: autodiscover.mycompany.local and autodiscover.mycompany.co.za both of which resolved to the internal IP of the exchange server. The public DNS A record for autodiscover.mycompany.co.za pointed to my TMG.
So in attempt to point my autodiscover records to Office 365 I deleted those 2 static A records from the on-prem DNS server. I then changed the public facing DNS record for autodiscover and pointed it to Office 365. The problem now is that within the LAN autodiscover.mycompany.co.za is not resolving.
But specifically in your case you deleted AutoDiscover from your internal DNS zone of mycompany.co.za so you cannot resolve that record inside the company. You need either to have a cname for AutoDiscover inside that DNS zone or do as @vasil says and point AutoDiscover at your onprem Exchange management server