Your recipients can report email as spam from their email client. You would have likely seen the option to do the same in your own email client. When a recipient marks your email as spam it will be registered in your SendYourMedia account as a complaint. If the recipient is in one of your address books, their email will be immediately moved to the cleaned list.
You should take an abuse report as a warning that people are complaining about your campaigns. If you get more complaints than a small handful, you should be concerned. We highly recommended re-evaluating your email marketing process to prevent further complaints.
Once abuse complaints exceed our threshold, you will receive a warning notice and sending from that address book will be paused. If the complaint rate is far beyond that threshold, an account suspension notice will arrive in your inbox from our abuse team. They will ask about your list collection process and ask for other details about the health and life of your email lists. We will need that information because by then ISPs and anti-spam organizations are threatening to blacklist us unless we explain why your list generated so many complaints. A full investigation will proceed once we have the requested information from you.
Even if you are a legitimate marketer who does everything correctly and only uses opt-in lists, you can still get reported for spamming. Even if someone has signed up to receive emails from you, they can click the spam button in their email application if they think it's spam or junk mail. Some people just think the button is an easy way to unsubscribe from your list. Some people won't even scroll down and click your opt-out link. That is why a couple of complaints are understood, but several gets raises red flags.