If you sent as Plain text then the graphic is likely to get added as an attachment. It would be best to always send emails in both HTML and Plain text and let the recipient choose. But it is real pain if you are getting that pop up on a frequent basis. Check settings: * Menu app icon > Options * select 'Composition' Under 'HTML Style' section * click on 'Send Options' When sending messages in HTML format and one or more recipients are not listed as being able to receive HTML: I suspect you currently have the 'Ask me what to do' option selected. * Select 'Send the message in both plain text and HTML' * click on OK Otherwise you would have to create email for those who you know only want Plain Text and attach the image. Then create another email in HTML and either embed image in actual email or attach as file. Personally, I always attach as a file, but some people like the image to appear within the email content. Please note: In Thunderbird, email with image sent as an attachment can be shown as if inline at the bottom of the received email. But you have to select 'View' > 'Display attachments inline' to switch it on. This is regardless of whether sending in plain text or HTML.