Using a Relay with SMPS as load leads to contact welding after keeping energized for sometime
Most of the electronics problems are due to imbalanced current and voltage calculations. You gotta consider the Relay rating for operating load using a relay. Look if e.g. your load requires 2-ampere and 230-volts, then you gotta use a relay with more(~50%) capacity say 3-ampere and 450-volts.(be on safe side :) ) Also you need to consider the copper thickness from external wire to relay NC-NO-COM pin on relay board.