Username and Sender addres do you have the same? "Send Test email to" must be different gmail address.

@Netbug After test I received email from gmail "A less secure application has been blocked" In account is necessary allow this less secure applications.

@Netbug Hello, working this setting: SMTP: aspmx.l.google.com port: 25 (without SSL) authentication: yes sent test email to - must be any gmail.com

@lexam Hello, I had the same problem: https://community.tp-link.com/en/business/forum/topic/265924

@WesleyB Hi, I don't understand why faulty firmware is still offered, why it's not removed. Pavel

Hello, I reboot router via Omada OC200, after restart adopting failed. Next I unpluged power to router. After restart adopting process was ok. Then upgrade fw via Omada, adopting ok. Correct router...