We are phasing out Zendesk. Please see Discourse instead: https://community.getmailspring.com/t/saving-message-drafts/253
Unsent drafts will be auto-saved to the Drafts folder as you write. You can view drafts for each of your accounts separately or together.
Any messages you’ve scheduled using the Send Later function will also be saved to your Drafts folder. You can edit the message at any point before the scheduled send time.