I know each user has a default "from/from email" but what Marketo user actually wants to send an email from them?
The admin should be able to create a universal default "from" and "from email" and even "reply-to" for every user. It would pre-load on every new email created so there is less chance of human error typing in the address every time.
Better yet, how about making those areas in the email editor a dropdown for a list of recent/most popular/preset values for each of those fields.
.png)