Email client programs are software applications that reside and run on the hard disk of a home computer / network. Therefore because they are client programs and email client programs uses resources from a client server (usually your Internet Service Provider) to beable to recieve and send new messages. There are automatic processes to setup an email account with a client program. For example in the cPanel X hosting application for Linux servers there is an auto process for outlook express. The options are as follows,

Auto-Configure Microsoft Outlook® for IMAP Access
Auto-Configure Microsoft Outlook® for POP3 Access
Auto-Configure Microsoft Outlook Express® for IMAP Access
Auto-Configure Microsoft Outlook Express® for POP3 Access

Manual Settings
Mail Server Username:
Incoming Mail Server:
Outgoing Mail Server: (server requires authentication)
Supported Incoming Mail Protocols: POP3, POP3S (SSL/TLS), IMAP, IMAPS (SSL/TLS)
Supported Outgoing Mail Protocols: SMTP, SMTPS (SSL/TLS)