offline message in chat application C#
<p>Hai. I'm developing an office messenger app just like Network assistant (http://www.gracebyte.com/nassi/). One of the features is broadcasting message to all contacts in network. but i have problem in sending message to offline contact. i mean if there's one (or more) of my contacts is offline, but i still wanna send message, how can i guarantee he'll get my message?</p>

<p>any of you knows the solution?
Oh i develop it using C#.</p>

<p>thank you :)
-ViNa</p>
