Invalid Hard Bounces

This article applies to:

What is an Invalid Hard Bounce?

When you try to send an email to an address that does not exist, the email provider will return an “Invalid Hard Bounce” response. This indicates the address is not deliverable and that future attempts to deliver email to that address will also fail.  Too many invalid hard bounces from an email marketer is indicative of poor email practices, which will harm your email sender reputation.

Unlike spam complaint rates, there is no real agreed upon industry standard rate when it comes to invalid hard bounces; the fewer the better.  At Infusionsoft, we consider anything over 5% per email provider as excessive and at risk for being contacted by the Email Compliance Team.

How Did Invalid Addresses End Up On My List?

Sending to a Cold Email List

30% of subscribers change their email address every year. If you don’t stay engaged with your subscribers, many will change their email address without you knowing. This results in old, invalid addresses on your list. Regular email sending is a great way to keep your list clean and helps prevent too many hard bounces.

If you have email addresses that have not been sent to for more than 4 months, you run the risk of sending to invalid addresses. Use caution when considering email marketing to cold contacts.

Purchased or Scraped List

Generate all email lists organically through lead collection.  Any account known to have imported a purchased or scraped list is in danger of having their account suspended.

Poor Lead Generation Practices

We’ve seen fake email addresses purposely entered into web forms to get to the promised reward like an ebook or access to exclusive information. This typically happens when the potential customer doesn’t trust the company behind the promotion.

List Bombing

List bombing happens when a web bot starts to randomly fill out all the web forms it can find with email addresses from who knows where.  Obviously this can be very destructive for email marketers for a number of reasons.

Why Invalid Hard Bounces Matter

Invalid Hard Bounces are considered a symptom of poor email collection and bad email marketing practices.  As mentioned above, too many Invalid Hard Bounces will damage your sender reputation and make it harder to deliver emails to the inbox.


If you have received an email from the Keap Compliance Team about excessive invalid hard bounces being generated by your application then please read this section carefully and enact the measures needed to reduce your hard bounce rate.

  • Perform List Hygiene - We recommend removing any contacts from broadcasts or automations that have been unengaged for > 12 months and contacting directly and contacts that have been unengaged for 6-12 months.  Identify unengaged contacts in your list by:
    • Login to your application.
    • Navigate to Reports > Email engagement tracker
    • Sort by Time Since Last Engagement
    • Select all contacts that have a Time Since Last Engagement value of over 12 months
      • Go to Action dropdown and select Update Opt-In/Out Status
      • Select Opt-Out and Process Action.
    • Return to the Email engagement tracker Report
    • Select all contacts that have a Time Since Last Engagement value of 6-12 months
    • Go to Actions dropdown and Apply a Tag so these can be found easily later -
      • Create a new tag, i.e., Bad Engagement, and then select the Apply radio button and then Save
    • Go to Contacts > Contact Lists > Create A List > Add Filter; Other Fields - Tags
    • Select Includes Any and enter the tag name just created 
    • Enter a name for this list i.e., Clean Up Engagement
    • For each of these contacts, go into the Contact Record and remove any tags (Other > Tags) for upcoming broadcasts and if necessary remove them from any automations. 
  • Audit your landing pages and check for unsecured web forms
  • Audit your lead collection process for incoming invalid email addresses and take the steps needed to promote trust and loyalty to your prospective leads
  • Review Email Marketing Best Practices Handbook and make improvements where necessary