Why is my email signature in outlook App (on Mac) suddenly adding my email signature icons as attachments?

Ok, the problem you have is probably due to an Outlook bug, at this point I release the question, maybe someone else has a solution.

Since you have confirmed that internal Windows users see the email correctly and the issue is isolated to the New Outlook app on Mac with external senders, you are likely dealing with a known rendering limitation in the new Mac client's handling of TNEF (Transport Neutral Encapsulation Format).

External users sending from Windows environments often unknowingly transmit emails in a Rich Text format that the "New Outlook" engine—which uses a web-based sync architecture distinct from the Classic version—struggles to decode, causing it to strip embedded images from the body and dump them as separate .png attachments.

To resolve this, you should first test by toggling the "New Outlook" switch in the top corner of your window to revert to the Legacy/Classic interface; if the signature renders correctly there, the problem is definitively a bug in the New Outlook's current rendering engine rather than your settings. Additionally, if this happens when you reply, you must ensure your signature was not created by copy-pasting images directly into the editor.

The New Outlook requires that you delete the current signature and recreate it strictly using the "Insert Picture" button (selecting a file from your hard drive), as copy-pasted images are frequently treated as non-embedded attachments when crossing into external mail domains.

If you want, you can send a feedback directly to New Outlook Dev Team

https://support.microsoft.com/en-us/office/contact-support-and-provide-feedback-in-new-outlook-for-windows-4a4bcc80-c71e-4e44-97c1-d0e62452ef4a

Hi Sharma, welcome in community

In addition of AI answers, keep in mind that this issue can occurs because the email format is inadvertently switching from HTML to Plain Text or Rich Text. Since Plain Text cannot support embedded images (like your logo or social icons) within the body of the message, Outlook strips them out of the signature layout and attaches them as separate files to ensure the recipient still receives them.

To fix this globally, navigate to Outlook in your Mac's top menu bar, select Settings (or Preferences), click on Composing, and ensure that the default format for new messages is set to HTML.

However, if this only happens when you reply to specific people, the issue is likely that the original sender emailed you in Plain Text; Outlook defaults to replying in the same format as the received message.

In that specific reply window, you must go to the Options tab in the ribbon and manually toggle the format switch back to HTML, which will immediately force your signature images to embed correctly again.

Let me know how it goes

Elvis

I tried what you mentioned above, but it was not useful, and I am still facing the issue. it's appear recent update.

It seems that the issue you are experiencing with your email signature in the Outlook app on Mac, where it breaks down into .png files or icons and adds them as attachments, may be related to how images in signatures are handled. In some cases, Outlook may treat images in email signatures as attachments if they are not embedded correctly or if there are issues with the signature settings.

You might want to check the following:

1. Ensure that the images used in your signature are properly embedded and not linked from an external source.
2. Verify that the signature settings in Outlook are configured correctly.
3. If this issue started after a recent update, it could be a bug that has been reported by other users as well.

If the problem persists, consider reaching out to Microsoft support for further assistance or checking for updates that might address this issue.

References:

• CodeTwo Signatures Add-in for Outlook (general)
• Office Add-ins known issues