MC 9.3.0 Email Gateway Settings

I'm trying to setup the email gateway in MC and there are two fields for SMTP Username and Password. However, our SMTP relay server is not configured to require a username/password in order for an application to send email. I left the fields blank and saved. However, when I click the test button, the error says
"Email configuration test failed. Exception reading response. please check mc log for details."

The MC log shows:
14 Feb 2020 15:18:46,304 [qtp386697093-110 - /webui/systemConfig/email/test?1581715272174] EmailServiceImp ERROR - Failed to Send Email to noreply@testemail.com, javax.mail.MessagingException, Exception reading response
javax.mail.MessagingException: Exception reading response;
nested exception is:
javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
at com.sun.mail.smtp.SMTPTransport.readServerResponse(SMTPTransport.java:1611)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1369)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:412)
Does anyone know if the the smtp username/password is a requirement for the MC to sent email?
If so, has anyone found a work around? Setting a username/password in our SMTP relay will cause many issues for the dozens of other apps that use it.
Thanks -
Dan