can't send SMTP test mail

[tung2000]

I'm using Cacti 0.8.7i with plugin architecture and thold plugin

I can't send test message using SMTP. I got the error as follows :
Unable to connect to SMTP Host 'mailhub.wharftt.com': (13) Permission denied

Then, I try to telnet to Cacti and then telnet to SMTP server port 25 to test SMTP operation by SMTP commands like helo, mail from: rcpt to:, data. I can get the e-mail.

Why Cacti can't send the test mail? Please advise.

Thanks!