Testing SMTP using telnet is tedious as you have to remember the commands and responses in the SMTP protocol. It gets even harder when doing SMTP AUTH, as then you have to base encode a bunch of strings [WayBack] How to Test SMTP AUTH using Telnet [Wiki] | NDCHost
Luckily there is a Perl script swaks: [WayBack] Swaks – Swiss Army Knife for SMTP which does ESMTP and LMTP as well as TLS.
The funny thing is that the repository at jetmore/swaks: Swaks – Swiss Army Knife for SMTP only has the readme, but the not the script which you can get from [WayBack] swaks.pl.
Despite that, most Linux distributions have an installation package.
[WayBack] swaks for OpenSuse is in the [WayBack] network repository, so for Tumbleweed (actually: Factory) on Raspberry Pi you need to perform this:
zypper addrepo http://download.opensuse.org/repositories/network/openSUSE_Factory_ARM/network.repo
zypper refresh
zypper install swaks
On Mac OS X it is even easier: if you have the homebrew package manager installed, you just install the [WayBack] swaks formula using the [WayBack] swaks.rb script:
brew install swaks
Note there is also the smtp-cli Perl script which I mentioned before at Fake/Mock SMTP servers and services for use during development, which also does TLS, but few environments have ready built packages for them. If you still want to try it out:
For SMTP AUTH:
swaks -tls --to jeroen.wiert.me@pluimers.com --from jeroen.wiert.me@pluimers.com --server smtp.xs4all.nl --auth-user username
Which prompts for the password, then outputs like this:
=== Trying smtp.xs4all.nl:25...
=== Connected to smtp.xs4all.nl.
<- 220 smtp-cloud3.xs4all.net ESMTP ESMTP server ready -> EHLO rmbpro1tbjwp
<- 250-smtp-cloud3.xs4all.net hello [188.206.68.219], pleased to meet you
<- 250-HELP
<- 250-AUTH LOGIN PLAIN
<- 250-SIZE 157286400
<- 250-8BITMIME
<- 250-STARTTLS
<- 250 OK -> STARTTLS
<- 220 Ready to start TLS === TLS started with cipher TLSv1:DHE-RSA-AES256-SHA:256 === TLS no local certificate set === TLS peer DN="/OU=Domain Control Validated/OU=PositiveSSL Wildcard/CN=*.xs4all.nl" ~> EHLO rmbpro1tbjwp
<~ 250-smtp-cloud3.xs4all.net hello [188.206.68.219], pleased to meet you
<~ 250-HELP
<~ 250-AUTH LOGIN PLAIN
<~ 250-SIZE 157286400
<~ 250-8BITMIME
<~ 250 OK ~> AUTH LOGIN
<~ 334 ############ ~> anA=
<~ 334 ############ ~> ############################
<~ 235 ... authentication succeeded ~> MAIL FROM:<jeroen.wiert.me@pluimers.com>
<~ 250 <jeroen.wiert.me@pluimers.com> sender ok
~> RCPT TO:<jeroen.wiert.me@pluimers.com>
<~ 250 <jeroen.wiert.me@pluimers.com> recipient ok
~> DATA
<~ 354 enter mail, end with "." on a line by itself ~> Date: Wed, 19 Jul 2017 09:09:57 +0200
~> To: jeroen.wiert.me@pluimers.com
~> From: jeroen.wiert.me@pluimers.com
~> Subject: test Wed, 19 Jul 2017 09:09:57 +0200
~> Message-Id: <20170719090957.052207@rmbpro1tbjwp>
~> X-Mailer: swaks v20170101.0 jetmore.org/john/code/swaks/
~>
~> This is a test mailing
~>
~> .
<~ 250 smtp-cloud3.xs4all.net accepted mail mXA71v00C4jr6ac01XA9Bo for delivery ~> QUIT
<~ 221 smtp-cloud3.xs4all.net ESMTP closing connection
=== Connection closed with remote host.
–jeroen
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