How to undo send in Gmail for up to 30 seconds

Even if you usually have excellent email habits, like always double-checking who’s in the “To” field, you’re only human. It’s natural to occasionally forget to link a file or notice you misspelled someone’s name after hitting “Send.” Thankfully, Gmail users have a built-in safety net that makes it easy to instantly undo sending an email.

Follow these simple steps to undo send an email and to extend your undo send window beyond the default five seconds.

Source