#!/bin/bash
#
cat <<EOF | nc smtp.server.com 25
HELO $(hostname)
AUTH LOGIN
loginBase64
passwordBase64
MAIL FROM: <user@server.com>
RCPT TO: <user@server.com>
DATA
From: no-reply <user@server.com>
To: Thiago <user@server.com>
Subject: Assunto da mensagem
Content-Type: text/plain; charset=UTF-8

Corpo da mensagem

.
QUIT
EOF