Gmail has a very useful experimental feature called "Cancel sending a letter", which allows you to cancel sending a letter immediately after it is sent. If you accidentally clicked on the “Send” button or remembered that you forgot to attach an important file, you have a few seconds to click on “Cancel” and continue editing the letter.
When this function only appeared in Gmail, you had 5 seconds to cancel sending a letter, but new intervals are gradually added: 10 seconds, 20 seconds and now 30 seconds. You can change the “time interval for canceling sending” on the settings page . ')