Outlook won't send when connected to orbi, does send connected to ATT router

This is the error message from outlook if I try to send while connected to the orbi router (wifi) if I switch back to the original ATT router (wifi) the messages send fine...what needs to change so I can use only the orbi router?

Send test email message: Outlook cannot connect to your outgoing (SMTP) email server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).