Marketing Email Delivered, then 4 weeks later Hard bounced (Unknown user) 550 5.1.10SOLVE
I am experiencing an issue sending marketing emails from HubSpot to certain email addresses. So far I have experienced this issue for 15 email addresses.
On Oct 23, 2020, I sent a marketing email successfully to these 15 email addresses. All marked as Delivered.
On Nov 13, 2020, I attempted to send another marketing email to these exact 15 email addresses. All Hard bounced (Unknown user):
Recipient's email address is invalid, misspelled, or blocking incoming email
UNKNOWN_USER smtp;550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup.
DNS provider was configured for both of the emails.
Why was the first email marked as Delivered and then the email sent 4 weeks later marked as Hard bounced (Unknown user)?
I'm cleaning up my customer contacts and I don't know how to handle these 15 based on the weird behaviour.
Solved! Go to Solution.
Email bounce reasons can be misleading, to say the least...
The first thing to clarify - are these 15 email addresses current customers of yours or prospective customers? The reason I ask is that the description of a hard bounce in your message is that the email address is either invalid OR "blocking incoming email". We've had several instances where existing customers haven't received emails sent via HubSpot (and indeed previous marketing email tools, such as CampaignMonitor), where they've had to allowlist us manually to receive our emails. Of course, you can't go asking prospective customers to do this, hence my question!
One other reason you can see this is if the recipient has set up forwarding for emails like this, or all emails, and the forwarding address is no longer valid. The email used could be valid, but forwarding marketing emails to a colleague who has left, or alternative invalid/mistyped email.
If these are active customers, I'd recommend contacting a small sample of them. If they're receiving one-to-one emails, but not marketing emails via the same address, I'd suggest getting their IT to add your email sending domain to their allow list (per https://knowledge.hubspot.com/email/contacts-not-receiving-your-marketing-emails).
Hope this helps!
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