It is more likely that the person who sent the email included the name with the email address when they sent the email to you. So this information is actually in the headers of that email which is now being used instead of 'Display name'. select email click on 'More' and select 'view source' a new window opens showing the source which will show what is in the 'From' header etc.

Basically Thunderbird will use whatever the sender put in the 'From' unless you override that by using your 'Address book' option 'Display' name.

Almost all senders include their "nice" name in their From field like "I am a gentleman" <badman@spammers.com> Thunderbird shows me "I am a gentleman" I want to see their real id badman@spammers.com. I can't go through millions of such entries in my address book to override the options for each individual. Thunderbird has the capability of extracting e-mail address from a string and can easily use it to display e-mail addresses but it seems it is not honoring my setting not to display name.

Try this add-on:

https://addons.mozilla.org/en-US/thunderbird/addon/show-address-only/

Despite the compatibility advice saying it's good up to TB 12, I have just downloaded and installed it into TB 56.0b2.

However, I have used this previously. I didn't like it myself. The display became too noisy, with it becoming harder to see and pick out known friendly correspondents.

My preference is to use another add-on:

https://addons.mozilla.org/en-US/thunderbird/addon/eaimh/

which allows me to see the true address in the message header.

I don't think it's hard to spot spam. I certainly wouldn't try to collect spam addresses in my address book, so the settings for display names or nicknames are hardly relevant.

Most phishing mails are quite obvious too, but the add-on makes it easier to verify from: addresses in the few messages that seem worthy of investigation. I like to report phishing attempts to the owner of the spoofed address.

So, is it a bug that despite the user preference to see e-mail address, thunderbird will not honor it?

Thunderbird shows you what is in the header. In the special case where a correspondent is known to you and is stored in your address book then you have the option of being shown his name as it appears in your address book rather than what the header provides. Since no same person would store spammers' addresses in his address book the "display name" option simply isn't relevant to you.

I've shown you two addons that reveal the true from: address. So why call it a bug?

The option is to switch off seeing your setting of 'Display' field in your contacts details within your address book. So thunderbird will use whatever the sender enters in the 'From' header. So your options are header info or your Contacts 'Display' name. Or try an addon as advised.

As junk mail should not be from any of your friends and correspondents, those 'junk' email addresses should not be in the address books. The 'Display' field is in the address book, hence why it is moot.

What you may need to check, setup/train is your Junk Controls. Then all junk (well most) will auto go into 'Junk'. You can set up your address books as whitelists, so allowing emails that are in your address books. see info: https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages http://kb.mozillazine.org/Junk_Mail_Controls