Spammy content: Sending unsolicited emails or spam can lead recipients to mark your emails as spam, which can harm your sender reputation. Poor email design: Emails that are not mobile-friendly, have broken links, or contain irrelevant content can frustrate recipients. Unclear opt-in process: Not having a clear and transparent opt-in process can make recipients feel tricked into subscribing. Frequent emailing: Bombarding your subscribers with too many emails can lead to fatigue and increased unsubscribe rates. Ignoring preferences: Failing to honor the preferences of your email recipients can result in a negative perception of your brand.