1. Higher Spam Rates: Without whitelisting, your emails are more likely to be flagged as spam, reducing their chances of reaching the intended recipients. 2. Poor Sender Reputation: Frequent flagging of your emails as spam can damage your sender reputation, making it difficult to maintain high deliverability rates. 3. Potential Blacklisting: Consistent issues with deliverability and spam can lead to your IP address being blacklisted, severely harming your email marketing efforts.