I’ve adapted this function to check for valid email address without connecting to the remote MTAs, since some of my hosts can’t create external SMTP connections.

I’ve also improved the regexp to allow for + and = mailbox delimiters, by substitute the regexp above for this:

“/^([a-zA-Z0-9])+([a-zA-Z0-9\.\\+=_-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/”