In the beginning.. there was mail, which was included in Unix 1st Edition in 1971 according to ancient texts (manuals). At this time, Unix had no remote communication facility at all, so mail would simply write to other users' files on a single machine. As systems began to be networked mailx came on the scene with expanded features. Eventually the two merged; these days mail and mailx are one and the same program and enjoy near-unversal presence across all flavors of Unix and Linux. For a bit more history of mail and mailx see the Heirloom Project.

One of the great features of mailx is it behaves like most traditional Unix commands; you can pipe the output of other commands to it or use it in a shell script or crontab. With just the default settings a user should be able to send a message to themselves or another account on the local system like so:

$ mailx localuser

The sender will generally be prompted to enter a Subject: after which they simply type their message then press CTRL+D to signal end of file (EOF) and off it goes.

To further automate sending simple messages the subject and an input file can generally be specified on the command line like so:

$ mailx -s “simple test” some_user < myfile''

Most mailx implementations allow multiple addressees as well as CC / BCC recipients to be specified on the command line which makes it's fairly easy to automate the sending of regular broadcast-type emails.