Undeliverable Notifications to "from:" address

Hi All,

I'm running a Java web application on a Linux box that uses javamail
and sendmail to send out emails. Our application has about 50 users
(sales reps from around the U.S.) and one of the features of the
application is to allow them to send files uploaded to the box as
attachments in emails to their clients. The application gives them a
web form for them to type in whom they want to send the email to,
choose the file to attach, and enter a message. When sending out the
email, for the "from" email address, we use the users' work email
address, which is from a different domain than our application.
Recently we have received complaints from users that, for messages
that do not get delivered, they were not receiving "undeliverable
notifications". I understand that the sending mail server is not
always in control of this, and our application is in a unique situation
because it does not control the domain of the email in the from
address, but I would like to implement this feature as much as I can if
possible. I do not want to implement this feature in Java but rather
want to implement it at the mail server level. Basically I would like
below to happen...

If the sendmail running on my box can determine that a message is
undeliverable (from either a bad URL, an unknown user, or a mail server
that's down), I want to send a message to the email in the "from"
address that their mail was unable to be sent. I also want to be able
to a) strip the email of the attachment and b) have some
customizability over the message that gets sent.

Am I biting off way more than I can chew? As you can see I am not a
sendmail expert but would like to implement this feature if possible.
I'd appreciate any help you can provide as my initial search in the
docs and on the web came up short.

Thanks,
Fred