This can have multiple causes:
- You are using a wireless network and the network periodically drops out, connect with a hardwired connection to verify.
- The server or user name under email notifications setup is the machine or SL user you are logging into or as. If you use a server name, there should be only one instance of SL running on that machine. If you use a user name, ensure it is dedicated for the task and that it is not in use by a user.
- You are experiencing network connectivity problems between the desktop and the server, verify on the server if such problems exist.