I sent out an email last week to over 300 contacts at various companies. It's clear that it only reached people at our internal company and not any of the other companies. The 'sent' address isn't the same as our internal company's address, and it was verified.
Hubspot reports however that it sent to those 300+ people with only minimal bounce backs.
What else can I do/check? I think it's unlikely that HubSpot is blocked at all those companies.