About

Linux runs a “locally configured” mailer daemon that doesn't route messages by default through the Internet but only copies messages to other users spool directories

It is real SMTP-compliant email, it's just not routed over the Internet without configuration.

Locally email client send mail to other local users on the system by addressing to user@hostname, or by just specifying the user.

Mail location

It can be found in the MAIL environment variable

echo $MAIL

/var/spool/mail/root

This is called a spool file. Standard location are:

• /var/mail/USER
• or /var/spool/mail/USER

Local Client

• mail (or Mail, mailx). Default
• What is Sendmail ?

#centos
yum install mailx

• mutt
• alpine
• less (to probe the file)

# shows the latest mails, at the end if the file
less +G $MAIL 
less +G /var/spool/mail/root

Configuration

The configuration is done via the mail transfer agent (MTA) to forward the messages to an mail address.

PAM has a mail module to set some configuration at login See pam_mail

The variable environment MAIL set the path of a mailbox

MAIL=/var/spool/mail/nico