Nearly one in four email addresses in a company’s database becomes invalid or risky within a year, according to the latest ZeroBounce Email List Decay Report.
Analyzing more than 11 billion email addresses verified between January and December 2025, ZeroBounce found that at least 23% of email lists degrade annually. While that marks an improvement from 28% in 2024, data decay remains a persistent challenge for businesses that rely on email to drive revenue and customer engagement.
Invalid email addresses remain the primary cause of decay. In 2025 alone, ZeroBounce identified more than 2.6 billion invalid emails and over 1 billion catch-all addresses, which can appear valid but still bounce and harm sender reputation. Abuse emails – contacts known for marking messages as spam – accounted for more than 155 million addresses. The platform also detected over 1 million spam traps and prevented more than 15 million potential bounces through real-time typo detection.
In total, only 62% of the email addresses submitted to ZeroBounce in 2025 were valid.
“Email remains one of the most powerful ways to reach customers, but the quality of your data determines whether your message reaches the inbox or disappears into spam,” says ZeroBounce founder and CEO Liviu Tanase. “Even a small percentage of invalid or risky contacts can damage sender reputation. Companies that prioritize email hygiene protect their deliverability and see stronger engagement as a result.”
Validating databases at least quarterly and verifying emails in real time at sign-up can significantly reduce the risk of emails landing in spam. Major mailbox providers like Google and Yahoo have strengthened their sender requirements, placing greater scrutiny on bounce rates, spam complaints, and overall list quality. At the same time, AI tools are increasingly shaping how inboxes filter and prioritize messages. Companies that fail to manage data hygiene risk seeing their emails filtered, deprioritized, or blocked altogether.
To create the 2026 Email List Decay Report, ZeroBounce analyzed the data it processed throughout 2025 across businesses of all sizes, from small companies to global enterprises.
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