See the last post…
https://www.esp8266.com/viewtopic.php?f=13&t=718
and in the Blynk Help docs…
http://help.blynk.cc/how-to-connect-different-hardware-with-blynk/arduino/esp8266-with-at-firmware
Adding commands to set the pins low within the BLYNK_WRITE (V3) function will have no effect on the startup state, as this function isn’t triggered until the V3 button is pressed, or you do a BlynkSyncVirtual(V3) command.
Also, you’ve stated that you want the relay to be off (LOW) on startup, not to synchronise with the current state of the button on V3.
You need a PinMode command, followed by a digitalWrite command in your void setup, to set the relay LOW on startup.
You also need to do a Blynk.VirtualWrite(V3, 0) after Blynk Connect to also set the switch widget to off, so that it’s in sync with the relay.
Pete.