We are installing campsite 2.1.7-rc2 on amin's server. Everything checks out during installation except the EVENT_HANDLERS module. When we define it to localhost or the IP address,we get:
Testing EVELT_HANDLERS configuration...ERROR
Error sending message: 552 sorry, your envelope sender domain must exist (#5.7.1)
We already tried localhost and IP address of the server but ended up with the same error.