Verification is not a deliverability test.

Side by side

Verification asks: should this address be mailed at all? It looks at syntax, the domain, MX records, and sometimes a short SMTP conversation. A good result means 'not obviously undeliverable.'

Deliverability asks: will the receiver accept this message from this sender and file it in the inbox? That depends on reputation, authentication, volume, content, and the recipient's own rules. A verified list can still go to spam.

Seed mailbox tests, when seed mailboxes are configured, report which folder those mailboxes filed the message in. That is not the same as every recipient's private filter. An open pixel is not a placement test, because filters and scanners load images.