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How come the new outlook client is inconsistent in its' rendering of emails

Marcus 0 Reputation points
2025-12-02T08:52:41.9333333+00:00

after spending about half a day on this issue, I understand that the old outlook client uses one rendering engine, and the new outlook client uses a browser based rendering engine (pretty unclear which one, though some seem to guess chromium).

Since there is a different rendering engine, I understand that some emails might look different, and I am not really complaining about that (you got to break some things to move forwards and improve I guess).

However, if it is true that the windows desktop client uses browser based rendering, how come it can't decide how to render things?

User's image

just have a look at that screenshot.

the one on the left adds paddings to the gray table, and it looks like I expect it to (coincidentally the same as in the old outlook).

On the right however it seems to forget that paddings are a thing, and that gray table looks pretty bad.

But it is the same email, in the same client. The only difference is that the left one is the view I get if I double click the email in the list to open it in a larger new window.

I mean it wouldn't make sense for outlook to pick different rendering engines for this, so what could possibly be causing this?

might be worth mentioning that it is a <table> with a class, whose css adds padding

Outlook | Windows | New Outlook for Windows | For business
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  1. Marcus 0 Reputation points
    2025-12-02T14:27:55.9533333+00:00

    I found the issue, and parts of the solution.
    When the email appears in outlook it looks perfectly fine.

    However there seems to be some form of background job that tries its best to inline all styles.

    in my case I had what I assumed to be pretty harmless style

    <style>
.my-class td {
padding-left: 15px;
padding-right: 15px
}
</style>

    However the job that removes my style does not seem to understand that type of nesting and simply ignores it.

    The 2 curious parts are why this job is being run to begin with (in the time between the mail arriving and this job being run, the email looks fine), and why the email viewer (double clicking the email and getting a new window) doesn't show the same version of the email without a style tag

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  1. Julie-Hu 7,105 Reputation points Microsoft External Staff Moderator
    2025-12-02T10:55:51.61+00:00

    Dear @Marcus, 

    Good day! Welcome to Microsoft Q&A forum! 

    Based on your description, I understand that you’re concerned about why the new Outlook for Windows shows the same email differently in the Reading Pane versus a pop‑out window, even though both should use the same browser-based rendering engine.

    I sincerely apologize for the inconvenience caused by this issue.

    Regarding this situation, this is likely because these two views use separate rendering contexts within the same browser-based engine. The Reading Pane applies stricter HTML/CSS sanitization for performance and security, while the pop‑out window runs with fewer restrictions.

    As a result, certain styles may not render consistently.

    For reference: Overview of the new Outlook for Windows

    When you have a moment, could you please kindly check if this difference occurs with other emails too? This will help us confirm whether it’s a general behavior or something specific to the HTML in that message.

    Kindly let me know when there are updates or if you need further assistance. Any updates you’re able to share would be really helpful. I appreciate your time and look forward to hearing how things are going! 

    Thank you for your time and patience.

    If you have extra questions about this answer, please click "Comment". 

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. 

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