Yes, and the first thing worth doing is confirming it, because most people assume spam when the real problem is somewhere else.
Send one email from your sending address to a Gmail address you control, and one to an Outlook or Hotmail address you control. Those two cover most of the companies you will be emailing and they behave differently from each other. Then look at where each one actually landed.
If they are really in spam, the causes I would check in this order: the sending address is new and has no sending history behind it, you went from nothing to dozens a day with no ramp, or you are sending from the same domain you are trying to sell.
If they are landing in the inbox and you are still getting no replies, then it is not a deliverability problem at all, and every hour spent on DNS records is wasted. Worth finding out which problem you actually have before changing any settings.