Why can&#x27;t the universal mail client I propose have a spam filter? More likely, my incoming mail server will have the spam filter; the client will have the spam folder. What does it matter if only SMTP messages end up in that folder?<p>&gt; Plus people want to filter differently. People deal with their inboxes uniquely.<p>That issue affects every messaging client&#x27;s filtering. How does it affect a client any differently if it combines, for example, SMTP and SMS?