You might try to elaborate on this topic, because I am confused. What undefined error has Photoshop given? This is the first I've heard of any of this. If an error message came from Photoshop, how does it tie into your email program which you say "checks out"? The only history of Mozilla Thunderbird email has had with Photoshop is, one instance of a PDF file attachment (nothing to do with Photoshop) that slowed email output and that was due to the size of the attachment.