About Bounces

Bounces occur when an email can't be delivered to an email address. When an email bounces, it is classified as either a soft or a hard bounce.
Below, you'll learn about types of bounces, guidelines for bounce limits, and how to handle high bounce rates.

Types of Bounces

Hard bounces are addresses denied for delivery due to invalid emails or an unexpected error during sending. Soft bounces are recognized by the recipient's mail server but are returned to the sender because the mailbox is either full or temporarily unavailable. Read about the differences between hard and soft bounces and how they're handled through our system.

ISPs and Bounce Rates

ISPs have set thresholds for bounces, unsubscribes, and abuse complaints that ESPs like MailChimp, are required to enforce. If these thresholds are exceeded, it could prompt a warning, or even an account suspension.
Thresholds fluctuate throughout the year based on the incoming send volume to a respective ISP's email domain. Because thresholds are in relative flux, and to avoid inadvertently assisting spammers, ISPs do not publicly release their threshold schedules. If you're taking proper steps to subscribe people to your list and practicing clean list-keeping, you shouldn't need to worry about exceeding these limits.

How to Reduce Bounce Rates

High bounce rates are often caused by lists that have gone stale, or addresses that were improperly entered or imported. Reconfirm your list to ensure your subscriber's interest and contact information is up to date. In general, we encourage you to use best practices while you maintain your list and to track subscriber engagement over time.

  • Use a double opt-in process
    Implement a double opt-in process to manage new subscribers. Accounts that use double opt-in experience fewer issues than those that use a single opt-in process. When you use double opt-in, you can be certain that the email address is valid.

  • Actively monitor subscriber engagementMonitor subscriber engagement to help you maintain a healthy list of subscribers, and use MailChimp tools to improve your content and win back inactive subscribers. List data such as member-activity ratings can help you track engagement.

Does MailChimp Manage my Bounces?

Yes. After you send with MailChimp, we remove undeliverable,  bounced addresses from your list. To prevent accidental imports of these undeliverable addresses in the future, we store them for each list.

However, there isn’t an account-wide suppression list. When you import to a new list, MailChimp can't block subscribers who bounced or unsubscribed from another list. For this reason, it’s a  best practice for list management to add new subscribers to your current list.

And although we manage bounced addresses for maintenance purposes, MailChimp is not a  list cleaning service. If you import an old or invalid list, you may see a high number of spam complaints, undeliverable messages, or unsubscribes. These can raise red flags in our system and lead to  account warnings.

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