It depends on whether the application supports SimpleMAPI commands, like TB. Getting it to work with any specific application is sometimes tricky, but you can try the methods explained in the kb article.

As an example, the command to email a pdf opened in Foxit Reader creates a new TB message with the pdf attached.

How do I find out if the application supports SimpleMAPI commands?

I think you would have to ask the developer of the application, but if it doesn't communicate with TB after you set TB as the default email program, that probably indicates it doesn't support SimpleMAPI.

I have the same problem. I've used Nitro PDF reader for years and, in every case until recently, when I have a pdf document open in Nitro and click "Send as email attachment", Thunderbird has opened with the document attached. For the past several days, Thunderbird has not opened in response to such a click. Also, for the same time period, Thunderbird's minimize, expand and x symbols in the upper right corner have been blacked out. They still function if clicked blindly, but they cannot be seen. Coincidence? Different problems? I need solutions for both.

For the icon problem, start in safe mode (hold Shift (Mac:Option) when you launch TB) and see if it helps. It may also be caused by the Windows theme you're using, or the equivalent for another OS.

Try resetting TB as the default email program, as described in the link in my first post, to see if it opens automatically from Nitro.

Does Nitro open properly if you open a pdf attachment in TB?

Started TB in Safe Mode and the symbols were blacked out. Did a reset of TB as the default email program. Restarted TB and it had made no difference. Double-clicking an attachment in TB does open the attachment in Nitro.

Another change that took place at around the same time as changes previously described is the necessity to provide User Account Control approval before TB will open. Other ideas?