Exchange 2007 Distribution Groups

we have a Exchange 2007 server, with many Dist Groups
there is one in particular Mail-Enabled Universal Distribution Group
that when staff sent a email to this group it has 100 external users and a few internal
a few of the external users had there out of office notifications on, so then what happened everyone in the dist group was getting these notifications...

is there something I did wrong in creating these groups?
some additional security settings that need to be done?  can one prevent others from replying to dist groups?  
Who is Participating?

Improve company productivity with a Business Account.Sign Up

OctInvConnect With a Mentor Commented:
Mail Flow Settings tab, then Message Delivery Restrictions properties, and as Adminmaster says, tick the box that states "Require that all Senders are authenticated".
its a checkbox in the distribution group properties
nutekconsultantsAuthor Commented:
hmmm, I am in the properties and do not see any checkbox, is there some specific tab?
octinv is correct . that is wht i meant. thx octinv .
Glad the solution worked for you Nutekconsultants. I think these should really Adminmaster's points as it was his suggestion, I simply expanded on it.  
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.