To change the server URL for an Exchange 2019 account to point to a different internal server, you typically need to update the Autodiscover settings, virtual directories, and possibly DNS records. Here's a step-by-step guide:

1. Update the Autodiscover Service
The Autodiscover service is responsible for providing clients with the correct server settings. You need to ensure the Autodiscover URL points to the new server.
Steps:
Open the Exchange Admin Center (EAC).
Navigate to Servers > Virtual Directories.
Select the server you want to update.
Click the Edit (pencil) icon for the Autodiscover virtual directory.
Update the internal and external URLs to point to the new server.
Save the changes.

2. Update Virtual Directories
Ensure all virtual directories (OWA, ECP, EWS, etc.) are configured with the correct URLs.
Steps:
In the EAC, go to Servers > Virtual Directories.
For each virtual directory (OWA, ECP, EWS, etc.), click the Edit (pencil) icon.
Update the internal and external URLs to reflect the new server.
Save the changes.

3. Update DNS Records
Update internal and external DNS records to point to the new server.
Internal DNS:
Update the Autodiscover and mail records to point to the new server's IP address or hostname.
External DNS:
Update the Autodiscover and mail records to point to the new server's external IP or hostname.

4. Update Client Configurations
If clients are manually configured, update their settings to point to the new server.
For Outlook clients:
If Autodiscover is working correctly, Outlook should automatically reconfigure itself.
If not, manually update the server settings in Outlook.

5. Test the Configuration
Use the Remote Connectivity Analyzer (https://testconnectivity.microsoft.com/) to verify Autodiscover and other services.
Test internal and external access to OWA, ECP, and other services.

6. Rebuild Offline Address Book (OAB) (if necessary)
If the OAB was hosted on the old server, you may need to rebuild it on the new server.

Steps:
In the EAC, go to Servers > Databases.
Select the mailbox database and click Edit.
Update the OAB settings to point to the new server.
Rebuild the OAB if necessary.

7. Monitor for Issues
After making the changes, monitor logs and client connectivity to ensure everything is functioning correctly.
Additional Notes:
If you're migrating to a new server, ensure all mailboxes and services have been moved to the new server before decommissioning the old one.
If you're using a load balancer, update the load balancer configuration to point to the new server.
By following these steps, you should be able to successfully point your Exchange 2019 account to a different internal server.