In Gmail, you can recall your message after you send out. By default, you have 20 seconds to recall it back, but you can change to 5 seconds, 10 seconds, or 30 seconds.
Step 1: Login your Gmail account (please refer here to open one if you do not have an account yet);
Step 2: In the Gmail account, click the "Setting" button from the right-top corner;
Step 3: Click the "Settings" command from the drop-down list;
Step 4: Click the "General" tab in the settings menu;
Step 5: In the "Undo send" section, change the cancellation period from 20 seconds to another number, e.g., 30 seconds.
Step 6: Click "Save Changes" at the bottom and you will have 30 seconds to recall your message after you send out.