Setup Sendmail in GNU/Linux.

sendmail_setup.md

Setup Sendmail in GNU/Linux 📫

Scope: Set up a general-purpose internetwork routing facility that supports Simple Mail Transfer Protocol (SMTP).

Dependencies

Install these packages first, per your operating system (OS):

CentOS, Fedora	Debian, Ubuntu
dnf install	apt-get install
sendmail-cf	sendmail-cf
mailutils	mailutils
sendmail	sendmail

Disable Sendmail daemon

Improve Sendmail security by turning it off.

systemctl stop sendmail

systemctl disable sendmail

Preflight checks

You'll need these.

• Check for required files:

ls /etc/mail/submit.*

should yield:

/etc/mail/submit.cf

/etc/mail/submit.mc

• Check for m4 processor:

which m4

should yield:

/usr/bin/m4

Build submit.cf file

The secret sauce.

• Backup submit.cf:

cp -pv /etc/mail/submit.cf /etc/mail/submit.cf.bak

• Create mysubmit.mc macro configuration file by copying default macro configuration file:

cp -pv /etc/mail/submit.mc /etc/mail/mysubmit.mc

• Modify mysubmit.mc,

replacing:

[127.0.0.1]

with:

mailhost

on the msp line so that is looks like this:

FEATURE(`msp', `mailhost')dnl

• Commit your change (from /etc/mail):

m4 mysubmit.mc > submit.cf

Modify /etc/hosts file

More goodness.

• List the host's IP & hostname (IPaddress hostname alias), e.g.:

127.0.1.1 foobar.psych.nyu.edu foobar foo

• List an SMTP client (choose 1):

128.122.112.26 calaf.cns.nyu.edu calaf mailhost 128.122.108.240 smtp.nyu.edu mailhost 216.165.47.33 smtp.nyu.edu nyu mailhost

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