Blank email for the recipient in Outlook

Mail
15

I just want to clarify what the problem is, what our workaround fixes, and what it cannot fix.

Here’s the bigger picture:

Outlook Classic uses the Microsoft Word rendering engine to compose emails instead of a web browser engine. This provides a lot of flexibility for text formatting, but it also means that Outlook Classic must convert its internal Word document format to HTML before sending a message. The quality of the generated HTML has historically been poor, and it has long caused compatibility issues in other email clients and webmail services.

Outlook Classic also uses HTML comments to store internal commands and metadata.

In the latest version of Outlook Classic, Microsoft introduced a new syntax for these internal comments. Unfortunately, the new syntax is invalid because it contains nested HTML comments, which are explicitly prohibited by the HTML specification.

When replying to such messages, eM Client strips the invalid nested portion of these HTML comments during processing. As a result, when the reply is later opened in Outlook Classic, part of the internal metadata stored in those comments is missing. Outlook Classic therefore displays the message as blank.

Once a reply has been sent from eM Client without those invalid nested comments, it will always appear blank in Outlook Classic. Interestingly, Outlook (New) and Outlook on the web display the same message correctly because they do not rely on the Word rendering engine or the internal commands stored in these HTML comments.

What does the workaround in eM Client 10.4.5642 do?

eM Client 10.4.5642 specifically detects these invalid nested HTML comments and preserves them unchanged when sending replies. This resolves the problem for all newly created replies.

However, it cannot repair replies that were already sent by earlier versions of eM Client. Those messages have already been modified, and the missing HTML comments cannot be reconstructed.

These older messages continue to display correctly in eM Client, Outlook (New), Outlook on the web, and virtually every other email client. The problem only occurs in Outlook Classic.

Broken scenario before eM Client 10.4.5642

  1. An email is sent from Outlook Classic and contains invalid nested HTML comments.
  2. The email is received in eM Client and displays correctly.
  3. A reply is composed and sent from eM Client. During processing, the invalid nested portion of the HTML comments is removed.
  4. The reply is received in Outlook Classic and appears blank because part of the original HTML comments is missing.

Fixed (workaround) scenario in eM Client 10.4.5642 and later

  1. An email is sent from Outlook Classic and contains invalid nested HTML comments.
  2. The email is received in eM Client and displays correctly.
  3. A reply is composed and sent from eM Client. eM Client preserves the invalid nested HTML comments unchanged.
  4. The reply is received in Outlook Classic and displays correctly.

Scenario that remains broken even after eM Client 10.4.5642

  1. An email is sent from Outlook Classic and contains invalid nested HTML comments.
  2. The email is received in an earlier version of eM Client and displays correctly.
  3. A reply is composed and sent from the earlier version of eM Client. During processing, the invalid nested portion of the HTML comments is removed.
  4. The reply is received in Outlook Classic and appears blank because part of the original HTML comments is missing.

The only way to “fix” replies that have already been sent with the nested HTML comments removed is to edit the affected messages manually.

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