After Drupal transfer drupal webform stopped sending email

i done a transfer all the files are same and but the drupal webform stopped sendning emails does anyone know where to look in the coding and what to change
on log message m getting this

Error sending e-mail from to : SMTP Error: Could not authenticate.

error

 

Mail server would not be configure properly.

 

You can use the SMTP module to get around any limitations a host has placed (such as requiring authentication):

http://drupal.org/project/smtp