If the image was stored on your computer, then I can tell you how it might have occurred.

Open Write type some email content then add image: 'Insert' > 'Image' you clicked on 'choose file' and selected an image from a folder on your computer.

If you do not select: 'Attach this image to the message', then you will only be attaching the file link - which is not much good if you need to display that image. So make sure you select: 'Attach this image to the message'.

Then make any other choices. click on OK to insert.

"Attach this image to the message" is always checked.

Doesn't that suggest the image file is sent as an attachment rather than in line? There is nothing attached.

Attaching should include the image, but only looking in the message source will confirm that. (ctrl+U)

An example of an included image is

--------------090607010804000506020105
Content-Type: image/gif;
name="263.gif"
Content-Transfer-Encoding: base64
Content-ID: <part1.04010208.05030005@gmail.com>
Content-Disposition: inline;
filename="263.gif"

This being followed by the actual data of the image.

In the message source that image is refered to as

cid:part1.04010208.05030005@gmail.com"

Referring to the Content Id from the image meta data

Can you confirm that the image you want to insert into the email, is actually stored on your computer.

Click on 'choose file' and selected an image from a folder on your computer. then something like this will be seen in the 'Image location' field. eg: file:///C:/Users/UserAccountName/Desktop/test%20doc%20dump/honey_the_peke.JPG

I'm on Windows Vista, so my file location address may look a bit different. After you 'choose file', what do you see in the 'Image location' field. Please copy paste the line into this forum question.

The image file is right where it was on the Desktop when I inserted it into the message.

Menu: Insert > Image > Choose File

I don't get what giving you the path to the image is going to do, but here you go.

file:///Users/mattwills/Desktop/20150913_180431.jpg

please confirm you have this setting: View > Message Body As > and select 'Original HTML'.

Please send me an email with an image (the email is in my profile, click my name) We will see if it is broken on receipt.

Matt: I do not use a Mac, so i'm unsure about the filename.

When I add an image, I see this eg: file:///C:/Users/ But the mac user seems to have this: file:///Users/

I note the hard drive letter is missing. Is it normal for a mac or could it be causing the 'broken' image?

If the image was on a different drive from the application, it would show that, for example file:///Volumes/DriveName/Folder/FileName.jpg.

I see a way to send you a private message through this system, but not a separate email address.

While the HFS and HFS+ file systems are Apple proprietary, the underlying principles are really the same for Linux, Unix and OSX That is the drive is mounted using a mount point. Drive letter are not used.

try https://support.mozilla.org/en-US/user/MattAuSupport