Scenario
You wish to use hotlinked images in your signatures, but Signature 365 defaults to using embedded images.
Reason
Certain mail apps — including the native iOS Mail client and Gmail — can interpret inline images as file attachments. When that happens, recipients may see unexpected attachments added to the message.
Solution
Warning!
This may cause recipients of your emails to see hotlinked images as a red X if they do not allow the downloading of external images
Signature 365 can be configured to use externally hosted (hotlinked) images instead of embedding them directly in the message. This setting is applied at tenant level and must be requested through the support team.
When enabled, every image inserted by Signature 365 will be referenced via a URL rather than embedded within the email itself. This applies to both client-side and server-side signatures.
For a detailed explanation of the differences, see Using hotlinked vs embedded images.
Configure Outlook to Stop Embedding Images
To prevent Outlook from embedding images, you’ll need to update a registry setting in Windows.
Warning!
Editing the Windows Registry incorrectly can cause system issues. Proceed carefully and consider backing up the relevant key before making changes
Steps
- Press Win + R, type regedit, and press Enter
- Navigate to:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\Mail
Outlook 2016, 2019, 2021, and Microsoft 365 Apps all use the internal version number 16.0
- Locate the value named: Send Pictures With Document
- Either:
- Delete the value entirely, or
- Set its value to 0
- Close the Registry Editor.
- Restart Outlook.
Once applied, Outlook will reference images via their hosted URL instead of embedding them directly in the email.