Back in the olden days of Buttondown (2018), we had a easter egg feature: if you emailed drafts at mg.buttondown.email, we would create a draft for you. It was a fun little feature that a couple people used and loved, but it was very hard to find — there wasn't a great place in the interface to highlight it.
Rather than fix this problem by either removing the feature entirely or carving out a space for it in the interface, we've doubled down. If you send an email to newsletters at mg.buttondown.email, that will create a full-on email for you. This means, if you so wish, you never have to log onto Buttondown at all except to check your analytics once in a while!
(A good caveat here: this will only work if you have a single newsletter associated with your email address. If you've got multiple newsletters, try using different email addresses for each one!)