Configure linux to send email to external addresses

Quick test if mailx is installed:

echo "test" | mail -s "test" user@example.com

Check if exim4 is installed (or if not, if another mail system is installed!)

Use dpkg to do the configuration:

dpkg-reconfigure exim4-config

Choices here are:

• internet site; mail is sent and received directly using SMTP
• mail sent by smarthost; received via SMTP or fetchmail
• mail sent by smarthost; no local mail
• local delivery only; not on a network
• no configuration at this time

Choose the second option (mail sent by smarthost; received via SMTP or fetchmail). Note that if you choose the third (no local mail) the system tries to send local mail (to root etc.) via the external server, which of course doesn't know about the system and complains…

Leave as default (i.e. the system FDQN)

Leave as default - normally

127.0.0.1 ; ::1

as we are not accepting mail from anywhere else

Leave as default (i.e. the system FDQN)

Leave as default (nothing)

The external mail server address

Normally don't bother with this

Normally no.

Normally default (mbox format in /var/mail/)

Normally no

On a standard Debian setup the /etc/aliases looks something like this:

aliases

mailer-daemon: postmaster
postmaster: root
nobody: root
hostmaster: root
usenet: root
news: root
webmaster: root
www: root
ftp: root
abuse: root
noc: root
security: root
root: someuser

where someuser is the user you set up as the non-root user with sudo privileges (unless root can log in directly). Change the someuser entry to the desired external address:

root: user@example.com

This isn't necessary for exim, but is for postfix and sendmail. Run:

newaliases

to generate the aliases database (normally /etc/mail/aliases.db)