The SMS LED on the RST100/ 200/310 keeps flashing after reading SMS. Why does the LED keep flashing?

The LED continues to flash when there are messages present, even if they have been read.  

To stop LED flashing, messages need to be deleted.  

This can be done with an Intelligent handset (or equivalent) plugged into the RJ45 port, or by using the Beam Management System software (Messages tab, click on “Clear Last SMS”).