Add menu (3-button) option when viewing an email that lets the user see the source (raw code) of an HTML-formatted message.
HTML formatted emails can pull some shenanigans, like presenting a text string that does not match the URL of a hyperlink. Long-tapping a hyperlink shows its URL but other tricks can be used, like putting the text string across cells in a table instead of between <A> and </A> tags. Users still might to view the HTML code (source) of an HTML-formatted emails for other reason, plus they may want to review the headers. Tracing an email's source means looking at the Received headers. There are many reasons to see the source of an email. The desktop Outlook lets users see the source. Mobile devices should be afforded the same safety and interrogation.
Maikel Lourenssen commented
this is the only way to separate the scammers from the real messages.
David . commented
On my laptop I use the view msg source option to look at sender details before opening, if I do not recognise the msg.