Hello @DAVIDM3 ,
I wasn't able to recreate the issue you're describing in your account. I tried multiple contact fields and search terms, and all of them returned the expected results. Are you able to provide a screencap of the issue occurring for you?
Since the period / dot makes it one cohesive element, just searching for "harth" wouldn't return anything since that's not a term on its own for the person's first or last name. The term you'd need to search for would need to at least be a.harth since that currently appears to be their email address, as well as their first name. If you want to at least search for the contact based on "harth," I'd recommend adding it as their first name or last name.
Is this new? Because prior to the latest changes to your website you could search for a name and if it featured anywhere within the email it would find it.