The "More" menu shows that sometimes when you're looking at a list of email. There's a bug in Yahoo Mail whether it shows that menu or the fuller one, when viewing a list of email. I find that if I click the first email then click inbox to see the list of email. Then it shows the limited menu you show there. But if I click any other email then click inbox, then it shows the fuller menu. But if you want to see the header of an email, there's no point being in inbox view.
Two things to try, to get the full menu
First thing to try
Open an email then the more menu should show this, and if not then test with opening a few different emails see if yahoo have a bug there too, but for me when viewing an email I always got the fuller menu.
Second thing to try
The first thing to try, doesn't seem to work for emails that are in threads (or at least not the one I'm currently looking at). But there is another more option at the bottom:
If you are using Google Chrome then Right Click anywhere in the message body and click on "Inspect Element". Now find the IFrame with class "messageArea". Right click on all content between <iframe> and </iframe> and and click on "Copy as HTML" button. Paste it on any text editor (like Notepad). This is the source of the message body.
Best Answer
The "More" menu shows that sometimes when you're looking at a list of email. There's a bug in Yahoo Mail whether it shows that menu or the fuller one, when viewing a list of email. I find that if I click the first email then click inbox to see the list of email. Then it shows the limited menu you show there. But if I click any other email then click inbox, then it shows the fuller menu. But if you want to see the header of an email, there's no point being in inbox view.
Two things to try, to get the full menu
First thing to try
Open an email then the more menu should show this, and if not then test with opening a few different emails see if yahoo have a bug there too, but for me when viewing an email I always got the fuller menu.
Second thing to try
The first thing to try, doesn't seem to work for emails that are in threads (or at least not the one I'm currently looking at). But there is another more option at the bottom: