See the Test SenderFull Documentation for more information.

How to run it

TestSender cannot tell your email system to "send us an email". If it could, think of the spam possibilities! So you will need to start TestSender by sending us an email.

See below for where to send the email and how to put your unique passcode on it.

For your convenience, this webpage gives you an option to automatically start the email with just a click.

Before using TestSender you may want to list in your list of allowed domains (whitelist us) so the report TestSender returns to you is not sent to your spam folder.

When running multiple TestSender tests, you can add notes in the Subject: line. Just enclose your passcode in parenthesis and we'll find it. For example:

Subject: Test number 12 (my passcode here) on Tuesday

This passcode only works once. You can refresh this page to receive another one.

What it does

When you send an email to the special address listed below with your unique passcode, TestSender performs all the steps that Internet email systems go through to receive email. It records every command and byte of data that your system sends and every answer and byte of data that our system replies back. TestSender does actually receive your email, and it learns as much about your system as it can in the process.

Because CheckTLS focuses on security, TestSender tries to establish a secure (TLS) connection with your system. Along with recording everything, it looks at the security of the your system for things like: certificate contents and signers, encryption algorithms, key lengths, hostname mis-matches, weak cyphers, etc.

What it shows

TestSender sends its results as a reply to the email you used to start the test. Results are in plain text so you can test from any email system.

The Results email shows details of the test and the complete communications log of the SMTP session. Various security items and any errors are highlighted so they are easy to find.

The reply email looks like:

From: CheckTLS Test Sender TLS (>
Subject: CheckTLS/email/test/From: SUCCESSFUL

SUCCESSFUL CheckTLS/email/test/From: result 
*	from: <>
*	via: []
*	on: 2017-02-08 19:47:28 EST
*	Subject: your.password
Your email was sent securely using TLS. 
(this email intentionally has limited formatting)

The transcript of the eMail SMTP session is below, with:
--> this is a line from your email system to us (~~> when encrypted)
<-- this is a line to your email system from us (<~~ when encrypted)
=== this is a line about the tls negotiation (cypher, cert, etc)
*** this is an error, warning, or info line that the test found

<-- 220 CheckTLS TestSender Wed, 08 Feb 2017 19:47:28 -0500
--> EHLO
<-- Hello  [], pleased to meet you
<-- 250-8BITMIME
<-- 250-STARTTLS
<-- 250 HELP
<-- 220 Ready to start TLS
====tls negotiation successful (cypher: DHE-RSA-AES256-GCM-SHA384, client cert: Subject Name: undefined;Issuer  Name: undefined;)
~~> EHLO
<~~ Hello  [], pleased to meet you
<~~ 250-8BITMIME
<~~ 250 HELP
~~> MAIL From:<>
<~~ 250 Ok - mail from
~~> RCPT To:<>
<~~ 250 Ok - recipient
~~> DATA
<~~ 354 Send data.  End with CRLF.CRLF
~~> Received: from MyPC ( [])
~~> 	(authenticated bits=0)
~~> 	by (8.14.7/8.14.7) with ESMTP id v190lRnP003920
~~> 	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO)
~~> 	for <>; Wed, 8 Feb 2017 19:47:27 -0500
~~> From: "CheckTLS Tester" <>
~~> To: <>
~~> Subject: your.password
~~> Date: Wed, 8 Feb 2017 19:47:26 -0500
~~> Message-ID: <040701d2826e$15c0dc60$41429520$>
~~> MIME-Version: 1.0
~~> Content-Type: multipart/alternative;
~~> 	boundary="----=_NextPart_000_0408_01D28244.2CEAFB70"
~~> X-Mailer: Microsoft Outlook 16.0
~~> Content-Language: en-us
~~> This is a multipart message in MIME format.
~~> ------=_NextPart_000_0408_01D28244.2CEAFB70
~~> Content-Type: text/plain;
~~> 	charset="us-ascii"
~~> Content-Transfer-Encoding: 7bit
~~> One line message.
~~> ------=_NextPart_000_0408_01D28244.2CEAFB70
~~> Content-Type: text/html;
~~> 	charset="us-ascii"
~~> Content-Transfer-Encoding: quoted-printable
~~> </head><body lang=3DEN-US><div><p>
~~> One line message.</p></div></body></html>
~~> ------=_NextPart_000_0408_01D28244.2CEAFB70--
~~> .
<~~ 250 Ok
~~> QUIT
<~~ 221 closing connection

See the Test SenderFull Documentation for more information.

Your test is setup.

Send an email to this address:

Put this passcode in the Subject: 4g8962z4c2zxn

For example:

Subject: 4g8962z4c2zxn

This is a test message.

If mail is setup in your browser, click here to start the email