What happens when an email from webform fails to deliver?
It throws an error and drop it on floor like below:

Warning: mail() [function.mail]: Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in DefaultMailSystem-&gt;mail() (line 76 of \modules\system\system.mail.inc).
Unable to send e-mail. Contact the site administrator if the problem persists.
Warning: mail() [function.mail]: Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in DefaultMailSystem-&gt;mail() (line 76 of \modules\system\system.mail.inc).
Unable to send e-mail. Contact the site administrator if the problem persists.