For me it depends on what "validity" means.
1.) Prevent typos etc. Regex or Mailgun or Kicksend is enough. 2.) Prevent bounces, prevent wrong signups one needs to do double opt in.
1.) Prevent typos etc. Regex or Mailgun or Kicksend is enough. 2.) Prevent bounces, prevent wrong signups one needs to do double opt in.
2.) I urge developers to step back and think about the requirements they get. Concerning those I would have thought what validity in this situation means, e.g. light validation in JS, send validation / validation list on the server etc.