How to enable or disable using Alias for Sending Emails for all the Exchange Online Users

Scenario:

You need to enable the users to send emails using their email Aliases.

Steps:

From the Exchange Admin Center, click on settings from the left pane then select the Mail Flow option. Now you can see the option to enable or disable the Turn on sending from aliases as shown below:

Note: Once you are done with the changes, It will take a few hours for the changes to reflect.