How do I use an alternate address when sending mail from my mail file?
When using your mail file, you can send mail from any one of your alias addresses.
Note: This feature requires Domino version 12.0.1 FP1 or higher. All
mail files should use the Domino 12 mail template.
Click Sent From Addresses section select Enable sending message from your email aliases.
and in theNext, click Compose and in the From field select the address to use from the dropdown list.