Hello @WABC28806 ,
There's a couple possibilities as far as what's going on. It's entirely possible that your contact's domain is filtering the email and not letting us know. Some ISP's and domains can keep an email from being delivered, without actually reporting it as a bounce. It's also possible that the email got sorted into the junk/spam folder or into the contact's Promotions / Marketing folder (this can pop up with Gmail / Gsuite especially).
If the email isn't in their junk/spam folder or promotions folder, then it may be worth reaching out to the contact, and setting up safelisting with them. Otherwise, I'd recommend reaching out to our Deliverability team to see if they have any additional insight regarding the specific contact or their domain.
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