Often time using an apostrophe in an email template will display funny to the person who receives the email. The issue is related to the web reader rather than the platform itself. It is best practice to use HTML to call symbols instead of using apostrophes. This article does a great job of explaining why.
Here is another article discussing this issue and why you should never use straight apostrophes in email templates.
This means you'll want to replace apostrophes with the HTML code to call this. This will guarantee emails display this symbol regardless of the browser you are using.
For “ Left double quotes: Use “
For ” Left double quotes: Use ”
For ’ Apostrophe: Use ’