How to send emails from server
This page show how to send emails from a server by connecting to an external SMTP server.
As a alternative, you can also check the complete guide on how to build an email server.
Prerequisite
You will need a SMTP server to send the email. The one of your regular email address will work perfectly.
Install
$ sudo apt install exim4-daemon-light bsd-mailx
Configure
Edit file /etc/exim4/update-exim4.conf.conf
dc_eximconfig_configtype='satellite'
dc_other_hostnames=''
dc_local_interfaces='127.0.0.1; ::1'
dc_readhost='example.org'
dc_relay_domains=''
dc_minimaldns='false'
dc_relay_nets=''
dc_smarthost='smtp.example.org::587'
CFILEMODE='644'
dc_use_split_config='true'
dc_hide_mailname='true'
dc_mailname_in_oh='true'
dc_localdelivery='mail_spool'
The line dc_smarthost need to be updated with the name of port of the smtp server that you will use.
Edit file /etc/exim4/passwd.client and add a line like
smtp.example.org:username:mYpa$$w0rd
Note: if smtp.example.org is a CNAME, you must use the destination of the CNAME in the passwd.client file.
$ host smtp.gmail.com
smtp.gmail.com is an alias for gmail-smtp-msa.l.google.com.
gmail-smtp-msa.l.google.com has address 74.125.206.108
gmail-smtp-msa.l.google.com has address 74.125.206.109
gmail-smtp-msa.l.google.com has IPv6 address 2a00:1450:400c:c04::6d
here you see on the first line that smtp.gmail.com is a CNAME (alias) to gmail-smtp-msa.l.google.com. In that case you can put *.google.com in the password file.
Finally, activate the new configuration using
$ sudo systemctl reload exim4.service
Test
$ echo "body" | mailx -s "subject" address@example.org
You should receive the email in your mailbox
