Is but used correctly here:
Please believe me when I say this, but we'd be out of business if we accepted all the used products sent back us that was past our return policy.
What does it mean in this sentence? Could someone please explain.
Yes, but the rest of the sentences is rather screwed up. Anyhow, the beginning clause is just a way to get the listener's attention, and the "but" serves as a bridge to what he really wants to say. Try:You don't really need the part of the sentence up to and including but.
Please believe me when I say this, but we wouldn't be able to stay in business if we accepted all the used products returned to us according our return policy.