Definitions for "Mail Client"
Mail Client is a program that allows you to send, read and reply to e-mail (such as Microsoft Outlook). While MailRules allows you to send e-mail it does not provide the functionality that allows you to read it, so, in most cases, you will still require a mail client to access the messages that MailRules ignores.
a computer program loaded on your desktop computer that enables you to communicate with a mail server
an application which enables the user to send, receive and organize electronic mail