If you've scheduled a mailing to send later, you can still make changes to it before it's sent:
This will move the mailing back to your saved drafts. On the "Emails" page, click Drafts, then click the email name to open it in the editor.
If you just need to change the scheduled send time, click Review & send in the editor to open the mailing details page so you can reset the send time. You'll also need to select your recipients again.
You can't stop, recall, or edit a sent email after it has left our servers. For a list of reminders to help prevent mistakes, see our pre-send checklist.