I sent 50 emails. 12 bounced despite SMTP 250 OK. Here's why.

A campaign of 50 cold outreach emails experienced a 24% bounce rate, with 12 messages failing despite all addresses returning SMTP 250 OK during verification. The user discovered that an SMTP handshake only confirms the receiving server accepted the envelope, not that the mailbox exists. To resolve this, the list was processed through a validator analyzing MX behavior, breach history, and provider identity, using a RapidAPI tool to investigate addresses like [email protected].