Verifying Custom Domain Email Addresses

Verification Challenges

Custom domain email presents the full spectrum of verification challenges. The underlying provider can be anything — Google Workspace, Microsoft 365, self-hosted, or smaller providers like Zoho, Fastmail, or Rackspace. Each behaves differently. The biggest challenge is catch-all: a significant percentage of business domains are configured as catch-all, meaning every address appears deliverable at the SMTP level. Without catch-all scoring, 20-40% of your B2B email addresses remain unverifiable by traditional methods.

How VeriMails Handles Custom Business Domains

VeriMails automatically detects the underlying email infrastructure for any domain and applies optimized verification logic. Major providers like Google Workspace and Microsoft 365 receive enhanced checks tailored to their platform. For catch-all domains, our proprietary scoring algorithm assigns a confidence score (0.0–1.0) for each address, turning “unknown” into actionable data. For non-catch-all domains, verification provides definitive valid/invalid results.

Tips for Custom Business Domains Verification

Custom domain verification accuracy depends heavily on the underlying provider and catch-all configuration. Non-catch-all domains verify with 95%+ accuracy regardless of provider. Catch-all domains benefit most from VeriMails' probability scoring — this is where we provide the most value compared to other verifiers. If you're verifying B2B lists, expect 20-40% of domains to be catch-all. VeriMails turns these from unknowns into actionable probability scores.

What Results to Expect

Custom domains (non-catch-all): 95%+ definitive valid/invalid. Custom domains (catch-all): confidence scores (0.0–1.0) per address. Provider detection accuracy: 99%+. Overall, custom domain verification is VeriMails' strongest use case because catch-all scoring delivers the most incremental value here.

Frequently Asked Questions