Email garbage how do we stop it?

My husband is getting dumped on with email; most are similar to this:

From: Mail Delivery System [MAILER-DAEMON@anvar.fr]
To: gpfj@marshallunderwater.com
Subject: Undelivered Mail Returned to Sender

Attachments: This process will continue with two addtional public forum . . .

In the body of the message:
This is the Postfix program at host smtpav.anvar.fr.

I'm sorry to have to inform you that the message returned below could not be delivered to one or more destinations.

For further assistance, please send mail to

If you do so, please include this problem report. You can delete your own text from the message returned below.

The Postfix program

: connect to 10.41.1.243[10.41.1.243]: Connection refused

1. This makes it look like an email was sent to "gpfj@marshallunderwater.com" and bounced back.

2. NO SUCH email was sent from my husbands email account.

3. marshallunderwater.com is OUR company website ~ there is no such email addy as
"gpfj@marshallunderwater.com"

4. If it were just one, it wouldn't be a problem; he gets 60-70 every time he opens outlook

What to do?

arlene