when third party software sends email the logo part of the email signature doesn't appear.

I have a .jpg image in my email signature and it works fine. Recently our accounts receivable software added an email module. Like inside Thunderbird I set up an email signature inside the software. Also like inside Thunderbird the signature I created has a .jpg image. When I send an email through my software, though, the image part of my email signature doesn't get through. The person receiving the email gets the text part of my email signature but not the .jpg image. Is it possible the image is being blocked by Thunderbird. Like I said it works fine when the email is originated from Thunderbird.