SendMail with Office365 SMTP Relay

SendMail with Office365 SMTP Relay

// Update Packages
sudo apt-get update && sudo apt-get -y upgrade && sudo apt dist-upgrade -y && sudo apt-get autoremove -y

// Setup Hostname
hostnamectl set-hostname subdomain.domain.tld

// Create Host Record
sudo nano /etc/hosts

// Add this line
127.0.1.1 subdomain.domain.tld subdomain

// Install SendMail MTA and Mail Utilits
sudo apt install sendmail mailutils sasl2-bin libsasl2-modules

// Make Mail Dir if not exist
mkdir /etc/mail

// Create Mail Authentication Folder
mkdir -m 700 /etc/mail/authinfo/

// Update Access with Office365 SMTP User ID Pass
sudo nano /etc/mail/authinfo/office365-auth
AuthInfo: "U:root" "I:sender@domain.tld" "P:YOUR-PASSWORD"

// Generate hash file using Auth File
sudo makemap hash /etc/mail/authinfo.db < /etc/mail/authinfo/office365-auth

// Regenerate DB File
sudo makemap hash /etc/mail/access.db < /etc/mail/access

// Backup SendMail config File
sudo cp /etc/mail/sendmail.cf /etc/mail/sendmail_cf.backup && cp /etc/mail/sendmail.mc /etc/mail/sendmail_mc.backup

// Edit and Update Config File
sudo nano /etc/mail/sendmail.mc

## Office365 Config before last three line
define('SMART_HOST','[MX-OF-YOUR-OFFICE365-DOMAIN]')dnl
define('RELAY_MAILER_ARGS', 'TCP $h 25')dnl
define('ESMTP_MAILER_ARGS', 'TCP $h 25')dnl
define('confAUTH_OPTIONS', 'A p')dnl
define('confAUTH_MECHANISMS', 'EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
TRUST_AUTH_MECH('EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
FEATURE('authinfo', 'hash -o /etc/mail/authinfo.db')dnl

// Rebuild SendMail
sudo make -C /etc/mail

// Restart SendMail MTA
sudo /etc/init.d/sendmail restart

// Test Mail
/usr/sbin/sendmail -vf sender@domain.tld receiver@domain.tld
From: sender@domain.tld
To: receiver@domain.tld
Subject: Office365 SMTP Relay Test Email

This is a test message sent from Office365 SMTP Relay using Sendmail.

// Press Clt + D to Send