Why is my sent email delayed 30 seconds? Suspect DNS server.
Some email companies use to send emails in batches, so maybe every 5 minutes they send all emails, that were 'sent' in those last 5 minutes, or here 30 seconds. But almost no one does that anymore
gmail was a way to undo send, if the feature is enabled, where it just waits, 3 to 30 seconds, before sending the email. In that time you can hit a cancel button if you realized you've made a mistake.
Whats the domain (@applemail.com or what?), the mail client your using, are you sending the email to yourself, and anything you can tell us about your setup that might be buggered.