When you have completed editing your crontab file, exit your text editor as your normally would. Be sure to save the file you’ve just created (the crontab program will give the file a default name and location)
If you do not format your cron entry correctly, the cron program will notify you when you attempt to exit your editor.
You will then have the chance to fix the entry or exit your editor (which leaves the crontab file unmodified)
Provides interface for reading mail, writing new messages, and filing. Also called a mailer.
Examples: mail, Pine, Netscape Mail, Outlook.
Mail Transport Agent(MTA)
Routes mail from one user to another either locally or across systems.
Uses a transport protocol, usually SMTP (Simple Mail Transport Protocol), to provide the medium for mail transfer.
Examples: Sendmail, Qmail.
Mail Delivery Agent (MDA)
Takes a message once received at a site and gets it to the appropriate user mailbox.
Examples: procmail, mail.
Sample Exchange: Sending, Receiving and Retrieving Electronic Mail Workstation Workstation POP Server SMTP Server Mail Spool SMTP Server SMTP and POP Servers can be the same system Sending Mail Retrieving Mail SMTP Relay SMTP Connection POP Connection Receiving Mail MUA MTA MTA MDA MUA