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#!/bin/sh
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# File: smtp1.sh
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# Location: stackbin
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# Author: bgstack15
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# Startdate: 2024-08-05-2 14:05
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# SPDX-License-Identifier: GPL-3.0-only
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# Title: Send authenticated email with openssl s_client
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# Purpose: demo cli smtp auth
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# History:
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# References:
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# https://stackoverflow.com/questions/1546367/how-to-send-mail-with-to-cc-and-bcc
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# https://szclsya.me/posts/net/send-email-with-netcat/
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# https://serverfault.com/questions/1101104/how-to-send-an-email-with-openssl-and-microsoft-exchange-online
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# https://woshub.com/sending-email-via-telnet-using-smtp-authentication/
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# https://learn.microsoft.com/en-us/exchange/mail-flow/test-smtp-telnet?view=exchserver-2019
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# https://stackoverflow.com/questions/14640560/openssl-to-negotiate-ssl-encryption-for-starttls
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# https://thelinuxcode.com/openssl-s-client/
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# https://www.stevenrombauts.be/2018/12/test-smtp-with-telnet-or-openssl/
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# https://stackoverflow.com/questions/44250054/send-email-with-netcat
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# Improve:
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# Dependencies:
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# dep-fedora: openssl, coreutils
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# an smtp account and server
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# Documentation:
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slowcat() {
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while read REPLY ; do sleep .05; echo "$REPLY"; done
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}
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{
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message1="$( printf '%s' 'exampleuser@example.com' | base64 )"
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message2="$( cat ~/.config/smtp1 )"
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printf '%s\n' "EHLO exampleaddress.com"
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printf '%s\n' "AUTH LOGIN"
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printf '%s\n' "${message1}"
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printf '%s\n' "${message2}"
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# Everybody, so TO, CC, BCC is a RCPT TO. The To, CC, BCC headers are the decorations visible to the mail client.
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cat <<-EOF
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MAIL FROM:<exampleuser@example.com>
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RCPT TO:<user2@local.example.com>
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RCPT TO:<user3@anotherlocal.examplelong.com>
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DATA
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From: [marco polo] <exampleaddress.com>
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To: <user3@anotherlocal.examplelong.com>
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BCC: <user2@local.example.com>
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Date: Mon, 5 Aug 2024 17:31:32 +0000
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Subject: Hello from netcat
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sample message here
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.
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QUIT
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EOF
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# | slowcat | nc -v mail.example.net 587
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} | slowcat | openssl s_client -crlf -connect mail.example.net:587 -starttls smtp -ign_eof
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