Detail
Selecting this option stops the WorkgroupMail server from sending messages to the internet and it also stops the server downloading from ISP POP3 mailboxes.
NB The WorkgroupMail server will still receive messages sent from internal mail clients via SMTP, it will still receive incoming internet mail via SMTP (if it is so configured) and internal mail clients will still be able to download from their local POP3 mailboxes.