Configuring your Signature 365 Tenant to use hotlinked images

If you want to use hotlinked images in your signatures, Signature 365 can be configured to use externally hosted images instead of embedding them directly in the message. This can help because certain mail apps — including the native iOS Mail client and Gmail — can interpret inline images as file attachments, which can make recipients see unexpected attachments added to the message.

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

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.

Steps

1. Press Win + R, type regedit, and press Enter
2. Navigate to:

3. HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\Mail
   ``` :note[Outlook 2016, 2019, 2021, and Microsoft 365 Apps all use the internal version number **16.0**]
   
   

4. Locate the value named: Send Pictures With Document
5. Either:
   • Delete the value entirely, or
   • Set its value to 0
6. Close the Registry Editor.
7. Restart Outlook.

Once applied, Outlook will reference images via their hosted URL instead of embedding them directly in the email.