When I compose a message in Thunderbird that contains an inline base64-encoded image (for example, an HTML <img src="data:image/png;base64,...">), the image is correctly visible in the compose window. However, after sending the message: Other mail clients and devices display the inline base64 image correctly. In Thunderbird (both in Sent and Inbox folders), instead of the image there is just an empty placeholder/blank space. Steps to reproduce: Compose a new HTML message in Thunderbird. Insert an inline base64 image (e.g., copy-paste from clipboard or manually via <img src="data:image/png;base64,...">). Send the message. Open the sent message in Thunderbird or receive it on the same Thunderbird client. Actual result: The inline image is not displayed — only empty space is shown. Expected result: Thunderbird should correctly render base64-encoded inline images, as other clients do.