My SMTP working perfect.
There are 2 reasons SMTP isn't work in your RDP
1. Your RDP blocks send mail, lock port 25 and your RDP cant connect SMTP Server.
2. you configured wrong
It will take a lot of time to fix your RDP. I can't spend hours to fix RDP for you
Please buy RDP. It 's working OK. Open all port.
If you configured wrong. I will show you your wrong