Android users can undo sent emails through Gmail app :

Gmail has been allowing its undo send email option since 2015, giving users time to fix typos or attach forgotten files. But, now the company has also rolled out the feature for Android users using Gmail app on mobile phones. The feature is available on Gmail app version 8.7 and further versions of the app.
According to an Android Police report, the timing of the new undo is up in the air. However, testing has found that only versions 8.7 and forward have the feature. Even so, the feature does not show up for a few minutes at times on some versions, finally appearing only when the app is force killed or swiped out of memory. Multiple account support - Use both Gmail and non - Gmail addresses (Outlook.com, Yahoo Mail, or any other IMAP/POP email) right from the app.