As you mentioned "all manor of odd characters", I thought it'd be rude not to take a look...! The one I found which has (mildly) concerning connotations for me was https://mail.google.com/mail/e/B86 which is a padlock symbol. Seeing as how my (aged) mother in law's only understanding of internet security is "look for the padlock", this could (perhaps) be used to make an email look more legit and secure.

Thank goodness she doesn't have a gmail account!