HubSpot Ideas


Hubspot's unconventional bounce handling is costing us valuable leads and customers

Think about what the acquistion cost is for each new lead or customer for your business. What if Hubspot's bounce handling was quietly costing you hundreds (or thousands) of customers without your knowledge? That's precisely what I've found.

After receiving a steady stream emails in from subscribers over the last year complaining that they stopped receiving our emails yet hadn't unsubscribed, we discovered that unlike almost all other Marketing Automation vendors, Hubspot classifies mailbox full, policy and spam bounces as HARD BOUNCES.

I then found that 4,864 of my contacts had been removed from our mailing list due to these types of "hard bounces." After that, I reviewed the bounce policies for Eloqua (Oracle Marketing Cloud), Salesforce Marketing Cloud, Infusionsoft, Adobe Marketing Cloud, Marketo, Mailchimp, Act-on, Sendgrid, iContact Pro and Campaign Monitor. ALL of them classify mailbox full, policy and spam bounces as SOFT BOUNCES.

After contacting Hubspot regarding this, they did a mass unbounce of these contacts in July 2020. Since that time, I've gotten to review which of these contacts became active again.

Of our core, higest value customers, I found that 52% became active again (i.e. opening and clicking on emails and making purchases) within the first week of being unbounced. And as of Friday Sept 25th, when reviewing the overall list of the 4,864 unbounced contacts, 1,658 have become active again—which means 34% of these people never should have been hard bounced.

I invite you to create your own list of customers that Hubspot has removed from your mailing list by creating an active list with EMAIL HARD BOUNCE REASON set to Mailbox full, Spam or Policy. And when you see the results... please upvote this post and write to your Hubspot Customer Success Manager and demand this unconventional bounce handling be changed.  Because it is not helping your organization succeed.

13 Replies

This same issue has been happening quite frequently with our database as well.


This is affecting thousands of our contacts and is not allowing us to communicate to individuals wishing to be communicated to using your communication tool @hubspot


We've noticed this as well for one of our clients. We've created a hard bounce active list upon recommendation of @JLSB (thanks). We've added the other reason to the filter. Many of the hard bounces are categorized as "other". Anyone know what this would cover?


This is shocking and is meaning that we are having to prove to HubSpot that we have permission to send to our customers who pay to receive our communications.


Thanks @CHerbert and @smyth1492 

To give an update on this, I've been getting quite a bit of help from their product team on this issue and there is definitely a plan to address this. In the meantime, as stated in the original post, if you connect up with your Customer Success Manager there are some workarounds you can explore while a bigger fix is done.


@JLSB please can you provide some further information on the workarounds as our Customer Success Manager has been unable to get any info through the product team contacts that he has or anything about a plan to address.


thanks in advance


@smyth1492 we had to provide the Hubspot support team with evidence that email exchanges have taken place with one of our clients and a contact that had been globally bounced by Hubspot. They then "unbounced" that contact. 


@smyth1492 Ok here's what we are currently doing:


1) Based on an extensive review of our own false positives, we created an active list to find supsected false positives:

False Bounce Detection Active List.png

2) We then set up 3 custom contact properties:

Hard Bounces - Mailbox Full
Hard Bounces - Spam
Hard Bounces - Policy

3) We created a workflow which tallies these types of hard bounces, to prevent us from continuing to unbounce actual invalid contacts. Kind of like a "three strikes" system:

Increment Bounce Tally Workflow.png


3) We then have the Hubspot email deliverability team unbounce the suspected false positives which have re-bounced 5 or less times. Meaning, if a contact continues to bounce over and over again, we are not going continue unbouncing them. This is in keeping with a number of marketing automation platforms who hard bounce a contact after 5 soft bounces. 

Proposed Unbounce List.png

As a note, we use dedicated IP addresses so I believe that is part of why we were able to set this up.

I do know their product team is using the data from what we're doing to help roll out something more broadly. The above system is obviously not really scalable for a large number of Hubspot customers. But this might help you on an immediate basis.


@JLSB - thank you for this detailed information, very informative and helpful.


My problem is mostly with a my own contact. An email I wasn't using since much time and now is active again but Hubspot decided that I can't use it anymore, even if it now works again and I know it because I MANAGE IT. 

About the customers' bouncing addresses, yes, I think too that their way is not the best way to manage them. Anyway, I just don't use anymore Hubspot for marketing emails. I use an external service, I can't risk to have my account suspended because of bounces. It is so easy to have bounces. It would be too stupid.


Thank you for sharing your approach here @JLSB!


@JLSB we have still been going through very similar issues. We've been working with HubSpot email deliverability team to unbounce many false global bounces. We've also been working with a technical consultant. Have you had any update on your end of changes or solutions that might be rolled out?

Member | Partner

BTW, this is complicated even more by HubSpot's global bounces policy:


Global bounce: a hard bounce for a permanent reason across three or more HubSpot accounts. Permanent bounces include unknown user and mailbox full. Global bounces are dropped from future emails across all HubSpot accounts.


This happens even if you have a dedicated IP address. We've had to manually request thousands of email addresses to be made sendable again by proving they are still sendable. 


I understand why HubSpot is doing this ... to keep as high of an email reputation as possible ... but it's coming at the expense of being Draconian about list cleansing and hurting our lists by removing valid contacts.


Hello my friends at Hubspot, it has been about 2.5 years since I submitted this idea and upon checking this evening found another ~2,000 false positives of contacts in my database who have been erroneously labeled as invalid emails. It looks like the earlier cron which was set up has dropped out.

@Tom @jaleonard19 I would be very grateful for some thoughful and data driven solution to this issue rather than just hard bouncing a contact who registers mailbox full, despite opening the email immediately prior. They are clearly valid email addresses. How about contacts who returns mailbox full but have opened or clicked on an email in the last ___ sends do NOT get hard bounced after once instance, or some kind of logic like this?

Here is ChatGPT plus my comments IN CAPS:

Here are some key reasons why Hubspot and other email marketing vendors typically treat mailbox full as a soft bounce instead of a hard bounce:

  1. Temporary nature of the issue: A mailbox being full is often a temporary issue that can be resolved by the recipient deleting or archiving old emails. Treating it as a hard bounce could result in removing an email address from a list unnecessarily, whereas treating it as a soft bounce allows for continued attempts at delivery. GMAIL BOUNCES INCOMING EMAILS IF YOU EXCEED THE 15GB FREE LIMIT BETWEEN GMAIL, DRIVE AND PHOTOS. IT IS REALLY EASY FOR MOST USERS TO GET INTO THIS SITUATION.

  2. Possibility of future deliverability: Even if an email bounces due to a mailbox being full, it's possible that the recipient's mailbox will become available again in the future. Treating it as a soft bounce allows for continued attempts at delivery, while treating it as a hard bounce would result in permanently removing the email address from the list. THE STATISTICS I LISTED IN MY ORIGINAL POST DOCUMENT THIS.

  3. Maintaining email engagement: Treating mailbox full as a soft bounce helps maintain email engagement rates, as continued attempts at delivery allow for the recipient to eventually receive the email and potentially engage with the content. ENGAGED CUSTOMERS BEING REMOVED DUE TO FALSE POSITIVE HARD BOUNCES RESULTS IN LESS ENAGEMENT AND POORER DELIVERABILILTY OVERALL.

  4. Industry standard: Treating mailbox full as a soft bounce is a widely accepted industry standard, as it recognizes that the issue is usually temporary and allows for continued attempts at delivery. By following this standard, email marketing vendors can help ensure consistent delivery and avoid unnecessarily removing valid email addresses from lists. I ALREADY DOCUMENTED THAT EVERY MAJOR HUBSPOT COMPETITOR SOFT-BOUNCES THESE CONTACTS UP TO A CERTAIN LIMIT, THIS REALLY MATTERS.

    The same goes for spam and policy bounces, as covered in my original post! Please help!