Hello,
You have a third party extension that is causing this problem, it's adding the following:
span.icon-envelope::before, span.icon-mail::before {
content: "M";
}
I have no idea why that css would even be in there, it makes no sense to add something like that. The extension developer needs to correct this, it's coming from here:
http://www.fstore.cloud/index.php?option=com_ajax&plugin=arktypography&format=jsonOr simply disable that plugin.