Some e-mail display names are not showing in e-mail messages, just the e-mail address. How can I correct this?

You posted in the Firefox support fora queue. Firefox doesn't do email, it's strictly a web browser.

If you are using Firefox to access your mail, you are using "web-mail". You need to seek support from your service provider or a forum for that service.

If your problem is with Thunderbird, let us know and we can move this thread to the Thunderbird support queue.

Please post to Thunderbird.