Has anyone else seen a significant open rate shift after migrating to HubSpot?
We recently migrated our marketing automation platform to HubSpot (coming from a different system) and are working through the platform transition for email sending.
We run cold outreach as part of our marketing mix and have always sent from a shared IP, so this isn’t a new infrastructure change for us. Bot filtering is enabled, our sending infrastructure checks out, and we’re seeing ~75% inboxing via Validity — so the technical setup looks solid on our end.
That said, we’re seeing open rates that are lower than what we were used to on our previous platform, and we’re trying to understand how much of this is expected during a platform migration versus something we should be actively optimising.
A few things we’re curious about:
Did others experience an open rate dip after migrating to HubSpot, and how long did it take to stabilise?
For those doing cold outreach on a shared IP — any lessons learned on maintaining deliverability?
Any quick wins that made a meaningful difference in the first few months post-migration?
Happy to share more about our setup if it helps the conversation. Would love to hear from others who’ve been through something similar.
What stands out in your request is the mention of cold outreach. How exactly are you doing that? Have you warmed up your email sending (by, for example, gradually increasing volume)? What is the email volume in your case?
Yes, we warmed up as much as we could. First sending to engaged audiences then slowly increasing the volume. By cold outreach I mean that the majority of the list is from a specific source but not all of it. It’s a mix. And the volume is between 20k and 60k of contacts per send. Does it help?
@YulyaT what was the engagement like during warm up? What did the bounce rates and interaction rates look like? How long was the warm-up period? How is the email health tool rating your activity since starting email sending in HubSpot? Monitor email sending reputation with the email health tool
Which system did you use previously and what interaction rates did you see there? Do the two systems measure open rate, click rate etc exactly the same?
Moderator note: While this solution may not address the original poster’s specific situation, it could be helpful for other community members facing similar challenges.
During the migration period HubSpot clearly said that warm up is not necessarily since we already have an established domain (at least 2-3 years of sending from the previous platform Microsoft Dynamics). However, we still followed best practice and did a warm up for a month or so. The audience that we picked from the previous platform as engaged didn’t show any signals in HubSpot so this where we investigated how each platform measures regular email metrics. So the take away at this point is ok yes the platform measures differently but it just doesn’t make sense that it would be so drastic. We understand some sort of adjustment but not a drop in open rate of like 20 percentage points.
@YulyaT I don’t think I can offer help based on answers only to a few of my questions. Could you please revisit my previous reply and answer all questions?
what was the engagement like during warm up? What did the bounce rates and interaction rates look like? […] How is the email health tool rating your activity since starting email sending in HubSpot? Monitor email sending reputation with the email health tool
Which system did you use previously and what interaction rates did you see there? Do the two systems measure open rate, click rate etc exactly the same?
Ok. The engagement during warm up was mixed some groups had good metrics some not so good. Bounce rate was hitting HS limit about 5% max 8%. Email Health tool is rating everything as poorly that’s why we are investigating. And we used Microsoft Dynamics if you heard of it. Is that better?
@YulyaT what exactly does “mixed” mean? An 8% bounce rate alone during the warmup period could negatively affect the performance of the sends coming after.
What exactly is the email health tool rating poorly? What’s the current spam rate, bounce rate, unsubscribe rate?
Open and click rates are a consequence of the others - if you have a above benchmark bounce, spam and unsubscribe rate, and if Dynamics didn’t flag bot opens, this alone could explain what you’re seeing.
Regarding what to do next: Critically review the content of the emails, the audiences you’re sending it to, start validating email address to avoid bounces, maybe dial activity back and try to rebuild trust through highly relevant emails, explicitly requested by the recipients or sent to highly engaged contacts.
Mixed - meaning some emails had 20% and some 1%. Email health tool: Open rate is Poor, CTR is Needs work and Hard bounce is around 2% right now rated poor and unsubscribe rate is Excellent. That one buffles me.
Thanks for providing those additional numbers; they actually paint a very clear picture of what’s happening with your deliverability and why you’re seeing such a drastic shift.
Based on the metrics you shared, here is a breakdown of what is likely happening behind the scenes:
The 8% Bounce Rate is the Root Cause: In the email deliverability world, a hard bounce rate above 2% is a massive red flag, and hitting 5-8% during a “warmup” period is enough to severely damage your sending reputation right out of the gate. Inbox Service Providers (ISPs like Google and Yahoo) see those bounces, assume your list is poor quality, and immediately start routing your emails to the spam folder.
Why the Open Rate Dropped 20%: This is a combination of two things. First, because your sender reputation took a hit from the bounces, a large chunk of your emails are likely landing in spam folders (where they don’t get opened). Second, Microsoft Dynamics likely counted bot opens and security scanner pings as “real” opens. HubSpot has very strict bot filtering enabled by default, which gives you a more accurate (but inherently lower) true open rate. (According to Microsoft’s own documentation for Dynamics 365 Customer Insights (Journeys), their bot protection focuses strictly on link tracking. Microsoft explicitly states: “Bot protection doesn’t impact email or push notification open rates”. This means that when a corporate security firewall (like Mimecast or Proofpoint) or Apple Mail Privacy Protection (MPP) automatically pre-loaded your emails, Dynamics likely counted those automated machine actions as real, human opens.)
The “Excellent” Unsubscribe Rate Paradox: It’s completely normal to have an excellent unsubscribe rate on cold outreach that is performing poorly. Cold recipients rarely take the time to scroll down and click “unsubscribe.” Instead, they either ignore the email entirely or just click “Mark as Spam.” Plus, if the emails are already landing in the spam folder, they aren’t even seeing them to unsubscribe.
The Platform Mismatch: The most important thing to note here is that HubSpot’s Acceptable Use Policy strictly prohibits sending cold, non-opt-in emails. Because they use shared IPs for marketing emails, sending unverified cold lists puts the entire network at risk, which is why their system is heavily penalising your sends.
How to fix this moving forward:
Pause cold outreach in HubSpot: Stop sending to unverified, cold contacts immediately to prevent your account from being suspended.
Use a dedicated outbound tool: For your cold marketing mix, use a dedicated sales engagement platform (like Lemlist, Apollo, or Woodpecker) that sends through individual mailboxes rather than HubSpot’s marketing email tool. You can integrate these tools to sync the leads back into HubSpot once they reply or engage.
Clean your data: Run any lists you brought over from Dynamics through a verification tool (like Proofy.io, ZeroBounce or NeverBounce) before emailing them anywhere.
Rebuild your domain trust: For the next few weeks, only send marketing emails out of HubSpot to highly engaged contacts who have opted in and interacted with your brand recently. This will signal to ISPs that you send wanted mail and help recover your domain reputation.
I hope this helps you out. Please mark it as Solution Accepted and Like to help another Community member.
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