Can I send email through my mailgun subdomain at DO from email clients (not from the DO server itself)

I’ve configured postfix on my Digital Ocean droplet to relay mail through mailgun and that much is working. Is there a way for me to send mail to Mailgun email address from email clients other than the server I’ve configured postfix on?

I’m guessing I need to open up the “smtpd_relay_restrictions” settings in /etc/postfix/main.cf to do so, but then (if I’m not mistaken) that would let anyone relay mail through my DO/mailgun account.

Can I mitigate that by having a route just trash the mail that isn’t routed out to gmail or whatever?

Any help would be greatly appreciated.

Thank you.

Matt seriousfunk@gmail.com