Can I delete a note after sending it?

No. Even administrators can't remove a note from other people's views. Notes work like email: once a note is sent, each person deletes their own copy.

To delete a note you received, open it in Notes & Email, click Delete Note, then click Ok to confirm. If you sent it, you can delete it from your Sent Items tab the same way. That only clears it from your own list; everyone else keeps theirs.