someone had a similar issue to you:

their solution was to use jquery:

$(function() {
    $("a[href^=mailto:]").each(function(){  
        var sEmailAddress = $(this).text();
        $(this).replaceWith(sEmailAddress);
    });
});

Preventing SharePoint from converting email addresses to mailto links

someone had a similar issue to you:

their solution was to use jquery:

$(function() {
    $("a[href^=mailto:]").each(function(){  
        var sEmailAddress = $(this).text();
        $(this).replaceWith(sEmailAddress);
    });
});

Preventing SharePoint from converting email addresses to mailto links