Update KB4011123 fixes Outlook 2016 attachment bug

[German]Today, a little hint that might be helpful for administrators in corporate environments. Microsoft has released update KB4011123 for Outlook 2016, which fixes the attachment bug for mail forwarding.

What's the problem with Outlook 2016?

After installing the January 2018 patchday (01/09/2018), I guess, an annoying error occurs in Outlook 2016. If a user receives a plain text e-mail with an attachment and if he tries to forward this plain text message with the attachment to another e-mail recipient, the attachment is lost. There seems to be no problem with HTML mails. The problem is discussed within this expert-exchange.com post for instance.

Outlook 2016: Cannot forward attachments from Plain Text after Tuesday updates

Hello,
This is affecting all users in our organization.  If we have received an e-mail in plain text with an attachment, and attempt to forward that e-mail, Outlook strips the attachment.  It started today after Tuesday's updates.  The default option under "compose messages in this format" is set to HTML, but I have tried all options.  The attachment is immediately stripped after hitting the forward button.  If I go to Format Text on the forward, and change to HTML or Rich Text, it does not appear.  If I send the e-mail, the recipient does not have an attachment.
I have tried starting Outlook in safe mode, disabling various add-ins, repair installation, to no avail.

Also this Microsoft Answers forum thread addresses the issue of a missing attachment in forwarded plain text emails. Below you can see a screenshot with such a plain text e-mail including an attachment from the forum post.

(Source: MS Answers forum)

Forwarding this message to another recipient, ends with the result shown below.

(Source: MS Answers forum)

The attachment is stripped off and lost. This is a bug in Microsoft Outlook 2016. I guess, this issues happens often in environments, where scans a forwarded a pdf attachment via e-mail.

Update KB4011626 is causing this behavior

I found thjs reddit.com thread claiming update KB4011626 (Security Update for Outlook 2016: January 9, 2018) as a root cause for this behavior. I've mentioned this update briefly at Microsoft Patchday: Office, Flash, Windows (January 9, 2018), but did not see a warning about a known issue. The KB article has been revised on January 23, 2018, listing now the followings known issue:

Known issues in this security update

After you install this security update, attachments are removed when you forward plain text emails. To work around this issue, save the attachments locally, reattach, and then send the email.

1. Save the attachments to a temporary location.
2. Open the email, and then select Reply, Reply All, or Forward.
3. Add the attachments that you saved in step 1.
4. Send the email.

Update KB4011123 for Outlook 2016 fixes the bug

A mail from a German blog reader and some links within KB4011626 article, and also within the forum threads linked above pointing out, that Microsoft has released update KB4011123 for Outlook 2016 on January 22, 2018. The KB article says:

This update fixes an issue in which some attachments to plain text messages are removed when you forward the message.

Obviously the fix to the issues discussed above. The KB article points out that the update only applies to the. msi versions of Microsoft Office 2016 and Outlook 2016. The Click-to-Run versions of Office 2016/365 cannot be patched. The update is only available for manual download and subsequent manual installation in the Microsoft Download Center.

• Download update 4011123 for 32-bit version of Outlook 2016
• Download update 4011123 for 64-bit version of Outlook 2016

Further details may be obtained from KB article here.