7451 S/MIME Broken

Problem reported by Robert Simpson - 5/28/2020 at 9:10 AM

Resolved

Testing out MAPI with a digital signature today ... sent an e-mail via MAPI to my work account, and it appears botched on my work account (Office 365)

I digitally signed the e-mail and sent via SM Beta over MAPI. The received e-mail I got had a blank body, and a message that "Outlook blocked an unsafe atttachment file.tmp"

It looks OK in my Sent Items folder inside Outlook, but it's definitely NOT OK on the SM Web Interface Sent Items folder.

12 Replies

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Robert Simpson Replied

5/28/2020 at 9:25 AM

This is what it looks like in Outlook's Sent Items folder:

The above e-mail was sent with "Add a digital signature to this message" checked, but not the "Send this message as clear text signed" checked.

And this is what it looks like in the SM web interface Sent Items folder (raw data)

From: "Robert Simpson" <robert@domain.com>
To: <robert.simpson@workdomain.com>
Subject: Test
Date: Thu, 28 May 2020 09:06:50 -0700
Reply-To: robert@domain.com
Message-ID: <03dcdc0e83a840579eb7c7cc04010ac8@>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=fcc03c411c224a95a85703af64480075

This is a multipart message in MIME format.

--fcc03c411c224a95a85703af64480075
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable



--fcc03c411c224a95a85703af64480075
Content-Type: application/pkcs7-mime
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
	filename="file.tmp"

BASE64STRIPPEDOUT

--fcc03c411c224a95a85703af64480075--

There's quite a lot wrong with this. If I check the "Send this message as clear text signed" as well, I get a different output, but it's still wrong, and Exchange still can't understand it.

Robert Simpson Replied

5/28/2020 at 9:42 AM

Sending via EAS works fine. Raw data in SM Sent Items looks like this:

To: "Robert Simpson" <robert.simpson@workdomain.com>
Subject: Activesync signed test
Date: Thu, 28 May 2020 09:40:57 -0700
Message-ID: <01ef01d6350e$c36133f0$4a239bd0$@domain.com>
MIME-Version: 1.0
Content-Type: application/pkcs7-mime;
	smime-type=signed-data;
	name="smime.p7m"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
	filename="smime.p7m"
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AdY1DnWKzI5aeUdPSNSvJQ4r3eR3uw==
Content-Language: en-us
From: "Robert Simpson" <robert@domain.com>

BASE64STRIPPED

Larry Duran Replied

5/28/2020 at 12:35 PM

Employee Post

Hey Robert, thanks for reporting this. We'll be taking a look at it and we'll let you know what we find.

Larry Duran
Product Manager
SmarterTools Inc.
www.smartertools.com

Benjamin Breedlove Replied

5/31/2023 at 11:50 AM

It is May 30, 2023, what is the updated status on this problem?

Zach Sylvester Replied

5/31/2023 at 12:26 PM

Employee Post

Hey Benjamin,

Thanks for the question. This issue was resolved a long time ago.

Thanks,

Zach Sylvester

Software Developer
SmarterTools Inc.

www.smartertools.com

Oliver Replied

4/26/2024 at 10:16 AM

I'm a bit confused.

I have reported problems with S/MIME signed mails in Outlook connected via MAPI to the support. They told me that SM does not support S/MIME.

Christian Ressel Replied

2/2/2026 at 1:17 AM

Hello,

This is a slightly older issue. However, we've been experiencing significant problems with S/MIME on SmarterMail for several months now. Unfortunately, we haven't received any real feedback from support. As a result, we're losing more and more customers to M365, customers we painstakingly migrated from Exchange to SmarterMail. Incoming S/MIME emails are displayed as empty.

Oliver Replied

2/2/2026 at 2:22 AM

In the past, I had written to support a lot about S/MIME-signed emails. It was a bit tedious, but they were very helpful. After a few SM updates, sending and receiving S/MIME-signed emails works really well.

The only problem we still have is that S/MIME-signed emails from some senders arrive correctly, while others display a red bar at the top of the email and the message “The message content may have been altered.” However, the content of the emails is displayed correctly.

Christian Ressel Replied

2/2/2026 at 2:50 AM

It seems that all externally signed emails are arriving empty on our end.

Oliver Replied

2/2/2026 at 3:04 AM

Are you using the latest version of SM?

Christian Ressel Replied

2/2/2026 at 4:43 AM

We have installed all updates from the last few months, but the problem persists even with version 9526 (January 30, 2026). All email accounts on the Smartermail server are unable to read signed emails from external senders. The emails are then empty.

Oliver Replied

3/5/2026 at 7:59 AM

Today, I also received an email that had no message text in either Outlook or webmail. However, this message was not only signed with S/MIME, but also encrypted.

I was able to read a signed and encrypted S/MIME message from another sender.

The other big problem, however, is that when I reply to the message, I have to remove the encryption because SmarterMail does not support sending S/MIME encrypted messages.

S/MIME encryption is a recurring topic here in the forum. It is slowly becoming more and more of a problem for me, as more and more senders are encrypting their emails with S/MIME, to which I cannot reply in encrypted form. However, the other side requires me to encrypt my message as well!

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