Unable to send e-mail. Contact the site administrator if the problem persists When my web form is filled and submitted, I get redirected to a page that says:


  Thank you for submitting.


but theres a red warning box there that says:


  Unable to send e-mail. Contact the site administrator if the problem persists.


I think its the SMTP server, but I don't know how to fix that.
Try using:

SMTP Authentication Support

with
PHPMailer

If You use Gmail to set up STMP follow this steps:


SMTP server: smtp.gmail.com
SMTP port: 465
Use encrypted protocol:Use SSL
SMTP Authentication -- Your User Name and password
Leave the other options by Default