Apple Mail lets you schedule emails to send later and gives you a brief window to unsend a message after hitting send. Both features work on iPhone, iPad, and Mac.

Schedule Send Later

On iPhone or iPad

Write your email as usual
Long-press the send button (the blue arrow)
Tap Send Later…
Pick a date and time, then tap Done

The email moves to a Send Later mailbox where you can edit or cancel it before the scheduled time.

On Mac

Write your email as usual
Click the dropdown arrow next to the Send button (or right-click the Send button)
Select Send Later…
Pick a date and time, then click Schedule

You'll find your scheduled emails in the Send Later mailbox in the sidebar.

Undo Send

After tapping or clicking Send, a brief Undo Send banner appears at the bottom of the screen. Tap it to pull the email back before it actually leaves.

By default you get 10 seconds, but you can change it:

On iPhone or iPad

Settings → Apps → Mail → Undo Send Delay — choose 10, 20, or 30 seconds (or turn it off).

On Mac

Mail → Settings → Composing → Undo send delay — choose 10, 20, or 30 seconds (or turn it off).

Good to know

Schedule Send works offline — the email sends when your device reconnects, as long as it's powered on at the scheduled time.
You can reschedule or cancel from the Send Later mailbox at any time before it goes out.
Undo Send works for all accounts in Mail (iCloud, Gmail, Outlook, etc.) — it's a client-side delay, not a server feature.
These features require iOS 16 / iPadOS 16 / macOS Ventura or later.

For more details, see Apple's guides:

Send email in Mail on iPhone (includes Schedule with Send Later)
Unsend email with Undo Send on iPhone
Send an email in Mail on Mac (includes Schedule an email)
Unsend emails with Undo Send on Mac