Spam or HACKER?

Hello all. I am an IT guy and several of my customers have been getting weird emails lately. What makes them weird you ask, well these emails are failed delivery ones which seem odd since no one is at the machine or even in the office.

my first thought was the person just doesn't remember sending the email and typed the wrong address, well that isn't the case. This has begun to pop up on several more users, all at different companies. The email address seems to be real, I googled the address and they are real companies so my guess is someone has gotten into my server or the users machine and is using it to spam people. I am not sure what to do any ideas?

Here is a look at one of the emails.

From: System Administrator
Sent: Tuesday, April 29, 2008 7:30 AM
To: Melissa
Subject: Undeliverable: dvd Kick-up for sjammer

Your message did not reach some or all of the intended recipients.
Subject: dvd Kick-up for sjammer
Sent: 4/29/2008 5:57 AM
The following recipient(s) could not be reached:
sjammer@belcofp.com on 4/29/2008 8:23 AM
The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.
<belco-mail.belcofp.com #5.1.1>

 

I too have seen these sort of messages in the past.
My ISP told me that some spammers do indeed hijack your computer's email client to send these. They said they would take care of my problem and somehow they did.
I've not had any of these "undeliverable" notices since I reported the problem.
I can only suggest that you report these phony emails to your ISP.