Please note that only specially configured Internet email systems should pass this test; most systems should fail it. See Mandatory TLS for why this is so.


For systems that are specially configured to require TLS, this is a very useful test because it is a controlled "other end" for your system to send to.

How to run it

Just like TestSender, TestMandatorySender cannot tell your email system to "send us an email", so you will need to start TestMandatorySender 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 TestMandatorySender you may want to list in your list of allowed domains (whitelist us) so the report TestMandatorySender returns to you is not sent to your spam folder.

We cannot respond to Challenge-response email filters (e.g. SpamArrest, Support Sentry SpamBlock, iPermitMail) so you MUST manually allow mail from

When running multiple TestMandatorySender 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.

Note: A TestMandatorySender test may take 30 minutes to complete, and you should not have more than one test in progress at any given time. TestMandatorySender may have your email system try to send the test email more than once, so having more than one TestMandatorySender test in queue can confuse it.

What it does

When you send an email to the special address listed below, TestMandatorySender makes sure that Mandatory TLS is working. It does not invite your sender to use TLS and will not accept a STARTTLS command from your end. It instead tries to get your system to send the email as plain text.

If your system is correctly setup to require TLS, it must give up trying to send the email since we will not do TLS. Your system may then queue the mail to try again later. TestMandatorySender does accept the retry to clear the message from your queue, but the second try is not part of the test.

What it shows

TestSender sends its results as a reply to the email you used to start the test. Results have very limited HTML formatting so you can read them on 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. Because TestMandatorySender finds out quickly if your email will allow plain text, there is not much output in the communications log.

See Test Sender and Test Mandatory Sender for more information.

Your test is setup.

Send an email to this address:
Put this passcode in the Subject: 6pzkydr98mbdj

For example:
Subject: 6pzkydr98mbdj

This is a test message.

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

Be sure to whitelist (Expecially if you use a Challenge-response email service.)
Our test results can look like SPAM and we get many bounced results. If your test result does not come to your email in a minute or two, you can check our logs for a bounce from your domain HERE.