You can use email to communicate with users on your system and, if your installation is part of a network, with other users on the network. If you are connected to the Internet, you can communicate electronically with users around the world.
Email utilities differ from write in that email utilities can send a message when the recipient is not logged in. These utilities can also send the same message to more than one user at a time.
Many mail programs are available for OS X, including the original character-based mail program, Netscape/Mozilla mail, mail through emacs, pine, mutt, and Apple's Mail application.
You can use procmail to make any mail program easier to use and more secure. The procmail program (www.procmail.org) creates and maintains mail servers and mailing lists; preprocesses mail by sorting it into appropriate files and directories; starts various programs, depending on the characteristics of incoming mail; forwards mail; and so on. (Many of procmail's mail-sorting features are available natively in the Mail application.)
Many mail programs assume that mail is being delivered to a spool file on the local system, the traditional UNIX setup. The character-based mail program, for example, does not know about POP serversit just knows to look for a mailbox file in a standard location. By default a Mac OS X system is not set up for use with such mail clients.
If your system is part of a LAN, you can generally send mail to and receive mail from users on other systems on the LAN by using their login names. Someone sending Alex email on the Internet would need to specify his domain name (page 411) along with his login name. Use this address to send the author email: