Message entire network for maintenance

I am trying to find a way to send a notification to all users in the network to advise them of outages or maintenance. I have had no success using the msg service with windows 7, so I am wanting to see what other people are doing or using?
Josh RoweSystems AdministratorAsked:
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Ryan ChongBusiness Systems Analyst , ex-Senior Application EngineerCommented:
just send an email for notification? I thought this would be the most common practice.
Mal OsborneAlpha GeekCommented:
Some time over decade or so back, spammers noticed they could use the messenger service to spam users who didn't have a correctly set up firewall. This was common back then.

Microsoft's response was to leave the messenger service disabled by default, starting with XPSP2. L:ater versions of windows don't include it at all.
We can use msg.exe against a list of computers, so if you can create such a list, your problem is solved.
3 notes:
-msg.exe has to be executed with an account that has admin rights on all machines it contacts
-it needs to be used with the parameter /time:0 so that the message persists
-on the clients, we need to have the RPC ports (I think it's just port 135) open and also a registry entry set: HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server, set AllowRemoteRPC (DWord32) to 1 (needs a restart before it works).
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You can install 3rd party messaging software as an alternative to msg command. LAN messengers usually supports all Windows versions and provide  a broadcast option for users.
Here is an example
Josh RoweSystems AdministratorAuthor Commented:
Thanks for the info guys. @ Ryan, Yes I am aware we could send an email, which we do. This is more of a last notification type thing. So all users receive a message on their screen letting them know of something. Useful if they haven't read their emails for a while. @ McKnife, how do you get it to reference a user list? I tried messing with the registry key and that works, but it only allows me to message one user at a time? @ nobus, Yeah I saw that article as well, it only worked locally, unless I changed the registry setting McKnife mentioned, but even then I can only message one computer at a time. @ andgreen, I am open to using third party software, I tried LAN talk, but it needs a client to be loaded onto each PC, while I could this easily enough with SCCM, it would be better if there was something that could dynamically find each each logged on user or each pc and message them in one go.
"changed the registry setting McKnife mentioned, but even then I can only message one computer at a time." - will work against a list. The list can be retrieved if you simply ping an ip-range and write systems that are up to a file, like shown in

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Windows 7

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