<div>
Nope they are creating fresh new mail.
</div>


<div>
In Outlook it says (HTML) in window-title of the new mail. And it is received as plain text.
</div>


<div>
<div class="content wysiwyg-content">
Hi there,<br />
<br />
suddenly we are having some users, that have a weird Situation when sending internal mails to internal users.<br />
Randomly their mails are in plain-text mode and I have no clue where to search. Outlook is configured to create all mails as HTML.<br />
<br />
Any hint where to search for?
</div>
</div>


Hi there,

suddenly we are having some users, that have a weird Situation when sending internal mails to internal users.
Randomly their mails are in plain-text mode and I have no clue where to search. Outlook is configured to create all mails as HTML.

Any hint where to search for?

In Outlook it says (HTML) in window-title of the new mail. And it is received as plain text.

Exchange 2016 Outlook 201x plain-text problem

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

HTML (HyperText Markup Language) is the main markup language for creating web pages and other information to be displayed in a web browser, providing both the structure and content for what is sent from a web server through the use of tags. The current implementation of the HTML specification is HTML5.

HTML

Microsoft Outlook is a personal information manager from Microsoft, available as a part of the Microsoft Office suite. Although often used mainly as an email application, it also includes a calendar, task manager, contact manager, note-taker, journal, and web browser.