Catch-all domain detection with conservative handling

Catch-all domains accept email to any local-part regardless of whether the mailbox exists — xyz1234@company.com and alice@company.com both succeed MX verification. This makes MX checks alone insufficient for validating contact quality. Contacts from catch-all domains appear deliverable but frequently bounce or are read by nobody, because many catch-all configurations feed unrouted mail to a trash mailbox. Mixing catch-all addresses with fully verified contacts inflates your apparent list size while depressing engagement rates, producing misleading health metrics and campaign analytics.

Use an email validation API that returns a catch-all or accept_all status and store it on the contact record. Exclude catch-all addresses from cold outreach segments:

// Store validation status at ingest (example using ZeroBounce response shape):
await db.contact.upsert({
  where: { email },
  update: { validation_status: result.status },
  create: { email, validation_status: result.status }
})

// Exclude from cold campaigns:
const campaignContacts = await db.contact.findMany({
  where: {
    NOT: { validation_status: 'catch-all' }
  }
})

For budget-constrained situations, use the catch-all probe technique: during validation, send an SMTP RCPT TO command for a randomly generated address at the domain; if the server accepts it, flag the domain as catch-all. Many validation APIs perform this probe natively.