View and copy to the clipboard, deep links to emails and email headers, in the stock iOS Mail app by tapping and holding on an email in the email list of a MailBox folder.
Tap and hold on the left half to view/copy the email subject & deep link
Tap and hold on the right half to view/copy the email subject & deep link & headers.
You can also tap the edit button, select multiple emails and view/copy the subject & deep link. You cannot copy the headers when multiple emails are selected.