SQL & PL/SQL

Hi,
I am using utl_mail package to send email in html format.
I am able to send the emails successfully, but there is a delay in completion of my procedure holding utl_mail and delivery of the mail.
I guess the utl_mail.send will not wait for the mail to be completely delivered to the recipients mail box/ nor does this package return any output parameter.
How would i determine if the mail has been successfully sent to the concerned recipient?
Is there a log or an oracle table where in i can monitor/track mails sent through utl_mail.send.
Please also let me know if there are any specific defined exceptions for utl_mail package(ex: utl_file.invalid_mode)

I have been searchin for such information in books and documentations but with minimal use.
Please throw some light on this or direct me to any documents having these information.


Regards,
Hemant