Internal "All" Distribution List - Replied to by an outsider?!??!!?

Like most companies, we have an internal Ddistribution List on our Exchange 2003 server called "All".  It includes all of our internal employees, and no one else.  So.....One of our employees sent an email to this group today to schedule a company picnic.  About an hour later, she got a reply from some guy who she says she does not know, and who is not an employee of our comapny.  ??!!??HUH??!?!?  Is this possible?  How?  I'm the IT Manager (and helpdesk, and Systems Admin., etc...), so I have full control over our Exchange Server.  The reply wasn't so much Spam, as it was just saying "I'm really proud of that fantastic email you sent for the picnic, you must be proud of yourself".....

I'm thinking either one of our employees forwarded the email to another address and then replied as a joke, or someone someone left OWA open somewhere outside of the company or something.....

Any thoughts?  

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ryangormanConnect With a Mentor Commented:
Have you previously enabled Message Tracking? The Message Tracking Center within Exchange System Manager will allow you to see where the message was sent. You should expect to see a lot of "Delivered locally" for each internal mailbox and then a message for each external recipient that received the message.
It does seem like something like you already mentioned, i.e. a prank, or a former employee who is on the list by mistake etc. If you can't track down who sent the mail by looking at the mail headers, then the next best thing is to review the list membership and weed out anyone who does not belong.

It doesn't seem like a serious problem...
Yup try the headers to find out who has forwarded the mail to the external address.
This does not seem a real problem.
Unless someone replied from outside to your distribution list, that could cause some real havoc. you should only accept email from inside.
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Robberbaron (robr)Commented:
I have seen a couple of spam messages addressed to

So my distribution list is named like ~all.  (or something like that ;->)  
tenoverAuthor Commented:
Thanks for the comments, I'll dig a little deeper today.  How can I verify that I am "Only accepting email from inside" for my Distribution Lists?  I'e.: I do not want external people to be able to send email to my internal DLs!!  
In Active Directory User, right-click on the Distribution List, select Properties, then click on the Exchange General tab, and on that page you can restrict who can or cannot post to the list. A good start might be to "check" the box labeled "From Authenticated Users Only"
tenoverAuthor Commented:
Well, like everyone figured, the email had been forwarded to one of users boyfriend.  He replied to the sender of the message instead of just his girlfriend.  Thanks.
And yes, I had tracking enabled, and that's how I figured it out.  
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