[3.12] gh-120662: Improve `smtplib` example (GH-120668) (#120682)

gh-120662: Improve `smtplib` example (GH-120668)
(cherry picked from commit 4bc27abdbee88efcf9ada83de6e9e9a0e439edaf)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>