You mention HTML file. How did you create that file? Did you click on 'Write' and create the signature perhaps using a table to control layout in cells and rows, then save it as a HTML file and finally set up Account Settings selecting 'attach the signature from a file instead' and then choose that HTML file you created ? I have a folder in my desktop user account called 'Signatures' and it holds anything to do with signatures such as logos, images and html files I created using Thunderbird. Is your 'company logo' image stored on your computer in a similar way ? When you were creating the signature, you obviously had to add the logo image. Did you do this: * 'Insert' > 'Image' * click on 'Choose File' and locate the logo image * Select the checkbox 'Attach this image to the message' - it is important to select that option. * Add alternative text. * click on OK When completed did you use 'File' > 'Save as' and select 'File', so you could save as a HTML file in a suitable folder on desktop ? see images below as guide.