Sending emails requires you to set up and confirm a sender account. To add a sender, navigate to Settings > Email > Sender (you can also add a sender when you create a bulk email or proceed to distribute an engagement over email by clicking the “Add Sender” button under the “Sender Email” field).
You will need to enter a name for the sender (which will display in recipients’ mailboxes in the “From” field”), an active email address, and a street address. Once you fill out the form, you will receive a verification link in the mailbox of the email you entered; the address must be verified prior to being able to use it to send messages.
Note: Is your address not showing up, even though you went through the steps and verified it? Try pressing “Refresh senders” found under the “Sender Email” field.