Thanks for reply, its host at VM
behind a firewall, but I already verify that SMTP sever is accessible from Moodle VM.
To make sure the connectivity I use Power Shell & separate PHP page to send an email from same server using same SMTP settings and it is working fine .
Only Moodle is unable to send an email.
Moreover I try different smtp settings that's working perfectly in other applications but in Moodle its also fails and error message remains the same.
Error message remains the same " Your site couldn't communicate with your mail server. Please check your outgoing mail configuration.
Is there any way inside the Moodle that i can trouble shoot the issue. ?