Workaroun for internet security camera email (smtp) setting (my Trendnet IP422W)

the camera email test page prompt that: "Error: Email sending failed" (gmail, yahoo...)

My guess is that your camera, like most, doesn't provide SSL (secure sockets layer) encryption. Most e-mail providers that allow SMTP connections require this.
You'll have to download a tiny program, called Stunnel (thank you to the fine folks who created this and made it open source; the world owes you!) Here's the link to the .exe files:
http://www.stunnel.org/download/binaries.html
Install it, and open the file "stunnel.conf" in notepad. You don't need most of the stuff in there, so you can comment out the protocol for pop3 and imaps. You will need these lines:

client = yes

[ssmtp]
accept = 465
connect = smtp.gmail.com:465

"Accept" is the port that your camera sends the e-mail with (remember, an IP camera is actually a tiny computer). After you make these changes, run Stunnel (you can also set it to run as a service so that it starts every time Windows does.
"Connect" is the email server you want to connect to and the port that it accepts e-mails on. I've used gmail and it's default port in this example.

You're not done yet, though. You'll have to change the server in your camera settings from gmail's to the IP of your computer. Why? Because you'll need to send the e-mail from the camera to your computer first, where Stunnel will grab it and reroute it securely to gmail. If you don't know your computer's IP, grab it using ipconfig from the command prompt (available under Accesories in the Win XP start menu.

It works for me, at least !!