ProtonMail has useful features like scheduling emails, using short domains, sending expiring emails, and more.
Along with it, there is also the Undo send feature. It recalls sent messages and turns them back into drafts for editing. This feature is already on by default, and you can change the undo interval as needed.
Here is how:
Login to ProtonMail and click on Settings > Go to settings.
Choose PROTONMAIL > General from the sidebar.
Under the Messages section, the Undo send interval is displayed.
From the drop-down menu, choose from and between 0 to 20 seconds as the interval.
Once the message is sent, the Undo link is available at the top of the inbox.
Clicking on it recalls the message. It is then available in the ProtonMail composer window as a draft for further editing.
Besides this feature, the Messages section also has other useful options like keeping emails in the Sent/Drafts folder even if you move them to another folder. This option is disabled by default but can be enabled if needed.
Also, the Link confirmation option is on by default. It helps in protecting against unknown links in messages by displaying the full URLs before opening them.
Happy emailing.