The anatomy of an email address: what each part tells you about deliverability

The local part, domain, TLD, and MX records each carry signals about whether an address is deliverable. Understanding what to read and what to ignore is the foundation of good validation.

An email address is more than a string. Each component carries information about the sender, the infrastructure behind it, and the likelihood of successful delivery. Understanding what each part means helps you build better validation rules and interpret validation results more accurately.

The local part

The local part is everything before the @ symbol. It identifies the specific mailbox on the server. A few signals worth reading: very short local parts (under 3 characters) are uncommon for personal addresses. Numeric-heavy local parts (e.g. user84921) often indicate auto-generated accounts. Common words like 'info', 'admin', 'support' signal role accounts rather than personal inboxes.

The domain

The domain identifies the organisation or provider. Free consumer domains (gmail.com, yahoo.com, outlook.com) indicate personal addresses. Corporate domains suggest business contacts. Newly registered domains (under 90 days old) carry higher risk — they're disproportionately associated with spam, disposable services, and fraudulent sign-ups.

The TLD

The top-level domain (.com, .net, .io, .xyz) provides context. While there are legitimate businesses on every TLD, newer generic TLDs (.xyz, .top, .click, .link) have historically been associated with a higher proportion of spam domains due to their low registration costs. This is a signal, not a rule — always validate the full address rather than filtering by TLD alone.

MX records

MX records are the DNS entries that tell the world which mail server handles email for a domain. No MX record means the domain cannot receive email. Multiple MX records with different priorities indicate a properly configured mail infrastructure. A single MX record pointing to a known email provider (Google, Microsoft, Proofpoint) is a good signal.

The MX record check is the fastest and most reliable signal available. If there's no MX record, no amount of SMTP probing can save the address — it's INVALID, period.

Putting it all together

No single component is definitive on its own. A suspicious TLD combined with a newly registered domain combined with a numeric-heavy local part is a strong signal. A corporate domain with a proper MX record and a name-formatted local part is a strong positive signal. Validation is about aggregating these signals into a reliable verdict — which is exactly what OhBounce.ai does.