SendMail with Google Workspace SMTP Relay

SendMail with Google Workspace SMTP Relay

## Update Packages
sudo apt -y update && sudo apt -y upgrade && sudo apt -y dist-upgrade  && sudo apt -y autoremove 

## 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 -y

## Make Mail Dir if not exist
mkdir -p /etc/mail

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

## Update Access with Google SMTP User ID Pass
sudo nano /etc/mail/authinfo/googleworkspace-auth
AuthInfo: "U:root" "I:sender@domain.tld" "P:YOUR-PASSWORD" "M:LOGIN PLAIN"

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

## Google Workspace SMTP Relay
define(`SMART_HOST',`[smtp-relay.gmail.com]')dnl
define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
define(`ESMTP_MAILER_ARGS', `TCP $h 587')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: Google Workspace SMTP Relay Test Email

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

## Press Clt + D to Send