Is Gmail Undo pattern enough for bulk mailing? What are the better alternatives?

1. Does Gmail Undo Send actually work?
2. How do I Unsend an email on my phone?

Does Gmail Undo Send actually work?

The Undo send function is a default feature of Gmail. After you send an email in Gmail, you'll see the the undo option pop up on the bottom left of your screen. This allows you to recall the email. Click Undo to retract the email, and you'll be brought back to your draft.

How do I Unsend an email on my phone?

Right after you send a message, you'll see the message "Sent" and the option to Undo. Tap Undo.