I have a couple of prudent clients who I work with who have submitted plenty of lowball offers. I usually call the listing agent prior to submitting it to give them a heads up on what is coming in. I also tell them the amount just as a courtesy. I cannot control whether the listing agent will submit the offer or not but absolutely it is a duty for the agent to present the offer unless the seller has given the agent instructions otherwise. There are cases where a seller may tell an agent to not even present offers under a certain price.