Email address, simplified RFC 5322. The lookbehind pins the start of the local part and the domain is segmented label by label, which keeps the scan linear.
Label: EMAIL
(?<![A-Za-z0-9._%+-])[A-Za-z0-9._%+-]+@(?:[A-Za-z0-9-]+\.)+[A-Za-z]{2,}Write to john.doe@example.com for any question. → john.doe@example.comContact : support+billing@mail.example.org → support+billing@mail.example.orgnot an emailjohn@doeTags: international, contact