I have a site with many clients, some of which have been listed on the site for some time now 5 yrs +. When a visitor to my site contacts them, through a form based page a copy is sent to me and to the client. The senders email being the from and my site as a BCC. This is so that when my client hits reply that they are responding to the visitor that made the query. If the email address is inactive the visitor gets an error returned email, but I do not know of this. Over the years some of my clients have either lost or changed their email without informing me. Is there a way that I can run a check on the email address to see if it is still active? Only for when a client has been contacted through the system.