Setting up Email Exchange ActiveSync in Outlook 2019 - Office365

In Outlook 2019 with the latest Office 365 Make sure to do a manual setup:

1- In Outlook, click the File tab, then Account Settings.
2- Click the Add Account button.

3- Select Manual setup. or additional Server types, click Next

4- Select Exchange ActiveSync, click Next.

5- Server Settings:
Enter

• Your Name: Enter your name as you want it to appear to others
• Email address: your full email address
• Mail Server: Use the HIS server name: zmail.his.com so it will match the secure certificate installed on the server.
• Username: your full email address
• Password: Your current email account password
• Make sure "Remember password is checked"
• Offline settings: Click it to the left to select "1 month"

6- Click Next, let the server verify the information and create the account.
If you entered the correct credentials and everything is properly configured, you will see a complete status.

7- A sync process will then run automatically, and you will see your messages, contacts and calendar in Outlook once it is completed.

Note: The initial sync can take a while for big mailboxes (> 5 GB), so make sure to allow a few hours to a day to run.
In the meantime, have people access mail on their old computer or via webmail: https://zmail.his.com.