You shouldn’t focus only on serious offers.
A listing agent must follow legal and ethical duties and keep you informed of any offer on the house. But if you tell the listing agent that you’re not open to certain offers below a specific price, it might scare potential clients away.
It’s better to make sure the listing agent knows that you want to hear any offer they might receive, no matter how big or small. Moreover, you should insist on hearing all kinds of offers, more or less in the language of your listing agreement.
If you’re unlucky enough to work with an unscrupulous agent who only aims to get a higher commission, you might not hear about a lower offer. But that’s not always the case, as some trustworthy agents could act in your best interest and decide not to bother you with lower bids.
If you’re in a buyer’s market, you might want to reconsider offers that seem lower at first because they might end up better than you thought through negotiations and counteroffers.