Hi @Jaimin7,
I am not quite sure how your SMTP Server is configured, but everywhere I have implemented the PutEmail processors, I needed 5 mandatory properties:
1) SMTP Hostname
2) SMTP Port
3) SMTP Username (even though in NiFi it is not a mandatory field, it was a mandatory field for the STMP to allow the connection)
4) SMTP Password (even though in NiFi it is not a mandatory field, it was a mandatory field for the STMP to allow the connection)
5) From.
Having all these fields configured, I was able to send email from NiFi without any restrictions. Of course, I made sure that the firewall connection between NiFi and the SMTP Server is allowing such connections 🙂