Recently noticed a few people in our database marked as 'Email Invalid' with email invalid cause "551 5.7.0 [internal] recipient blackholed". Any explanation as to what exactly blackholed means would be really helpful.
Thank you in advance!
Probably very similar to "blacklisted". This means that whatever you do, your emails to this address will never reach the inbox, unless someone on their side removes your sender address from this blacklist.
Blackhole means someone really, really, REALLY dislikes emails from Marketo and sends an email to our privacy team requesting they be permanently blocked from being sent emails from all Marketo customers forever. The address may also be a known spam trap that we've blocked from mailing.
If you've verified the address is a real person, and that person wants their email to be removed from the blackhole, the Support team can work with the Privacy team to review the request.