When an email is rejected by a subscriber's email server, it's called a bounce. There are a few reasons and types of bounces, which you can find logged in your  campaign report. It's a good idea to keep a close eye on your bounce numbers to be sure your campaigns are reaching your susbscribers and that you're abiding by spam laws.

Hard Bounces

A hard bounce indicates a permanent reason an email cannot be delivered. Hard bounced email addresses are removed automatically and immediately from the active subscribers and placed in the Cleaned portion of your list. Cleaned subscribers will be excluded from future campaign sends to this list. While there are many reasons an email address may hard bounce, below are some common reasons this could happen.

  • Recipient email address does not exist.
  • Domain name does not exist.
  • Recipient email server has completely blocked delivery.


There are occasionally cases in which valid email addresses can hard bounce or a subscriber could  mistakenly unsubscribe.

Soft Bounces

Soft bounces typically indicate a temporary delivery issue to an address and are handled differently than hard bounces by MailChimp. When an email address soft bounces it means delivery to that address was attempted multiple times over the course of 3 days, but was not successful. After attempting delivery for those 3 days, we log the email address as a soft bounce on the campaign report. If that email address continues to soft bounce on subsequent campaigns, the address will eventually be considered a hard bounce and cleaned from your list. We'll allow 7 soft bounces for an email address with no subscriber activity and up to 15 soft bounces for subscribers with previous subscriber activity before converting a soft bounce into a hard bounce. While there are many reasons an email address may soft bounce, below are some common reasons this could happen.

  • Mailbox is full (over quota).
  • Recipient email server is down or offline.
  • Email message is too large.

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