alerted

two places to start for alerts...
you can download the sdk and start playing right away at:
http://www.microsoft.com/alerts

or if you want to use a hosted solution (no dev work for most scenarios so you can be sending alerts in 5 min) try:
www.messagecast.net

\matthew

Firewall error messages do not occur because of a lack of service capacity. There are many MSN Messenger firewall and proxy error messages. They arise from a wide array of scenarios. Overloaded corporate HTTP firewalls will occasionally drop MSN Messenger traffic without notifying MSN Messenger. Some home residential gateways will do this as well. Software firewalls can prevent Messenger from getting to the networking layer of the operating system (MSN Messenger will sometimes guess correctly that this is a firewall issue although it looks like there is no internet connection to the process). Many users simply misconfigure their proxy. For people consistently getting such an error message, we always recommend unchecking the "I use a proxy server" box in Options->Connections and let our automated logic try to connect to the service.

\matthew