High bounce rates are often caused by audiences that have gone stale, or addresses that were improperly entered or imported.
Internet service providers (ISPs) have limits for bounces, unsubscribes, and abuse complaints, and Mailchimp is required to enforce these limits. If these rates are too high, it could prompt a warning or suspension on your account.
Bounce rate limits vary between ISPs and email providers, and they change throughout the year based on incoming email volume. Because these limits are variable, and to avoid giving too much information to spammers, ISPs do not publicly release their limits.
How to avoid bounces
If you haven't sent a campaign in a while, reconfirm your audience to keep your contact information up to date. This should help protect your audience from spambots and fake signups that lead to bounces.
Yes. After you send an email campaign with Mailchimp, we track its delivery and clean bounced addresses from your audience. Email campaigns won't be sent to those addresses anymore, but you'll still be able to access them if you need to.
Sometimes hard bounces happen to valid email addresses. If a bounced address has recently engaged with your email campaigns, we won't remove it from your audience right away. The bounce will be noted in the contact's profile and count toward their contact rating as we keep an eye on future activity.
Although we manage bounced addresses for maintenance purposes, Mailchimp is not a contact cleaning service. If you import old or invalid contacts, addresses which bounced or unsubscribed previously could lead to a high number of spam complaints, undeliverable messages, or unsubscribes. To avoid these problems, follow best practices when adding or importing subscribers to your audience.