If you have set up an alias email address to forward your email to, you can have the option to choose what address a new email will be sent from. Just drop us a note in Help & Feedback (Main Menu > Help & Feedback > Still can't find what you need?) to start a new conversation with an agent, and tell us the alias email address.
Once we've made the update on our end, you'll be able to click the arrow next next to your default address, and select the email address you would like to use.
Whatever email address you select, your Karbon username will still appear as the sender on your recipient's end.