Have you seen.

• Applications panel - Set how Firefox handles different types of files

"Followed instructions for selecting an e-mail client ..."

That is strictly for the mailto hyperlinks used on some webpages to allow a viewer to send an email to the website or the author.
https://support.mozilla.org/en-US/kb/change-program-used-open-email-links

There is no "button" to open the selected email client from within Firefox. Back in the mid-00's Firefox did have a menu item for that, but the "connector" code in Windows was very flakey (worked less than half the time and was very unpredictable) so Mozilla just removed that feture due to Microsoft never seeing fit to fix it in WinXP. Over the years there have been a few different extensions which restored or added that feature to Firefox, but to my knowledge there hasn't been one for over two years now.

Thanks for your prompt response. I'm still confused. You've explained how I can't check/get/send e-mail via the Firefox Browser. Can you explain how I can do it? Cheers, Dave

Open Outlook Express, your email client.

Email clients, like Thunderbird and Outlook Express, do email. Web browsers, like Firefox, do the internet.

I don't know how to open Outlook Express without opening Internet Explorer first. After opening EI I click on the mail icon and Outlook Express opens and downloads mail from my Internet Provider's mail server. Using Internet Explorer to do this defeats the purpose of switching to Firefox. Thanks, Dave

Outlook Express is a seperate program, launch it from the start menu, it shouldnt load IE.

Thanks. I located it and put a short cut on my desktop. Never realized it was not part of IE. Cheers, Dave