How companies format email addresses
Most organisations pick one pattern and apply it to everyone. The most common by far is first.last, followed by first initial plus last name (jgarcia), first name only at small companies, and firstlast without a separator. Larger enterprises sometimes use last.first or add a middle initial to avoid collisions.
The practical trick is to find one confirmed address at the company, on a press release, a GitHub commit, a conference bio or a signature, and infer the pattern from it. Once you know the pattern, every other person at that company is one lookup away. This permutator gives you the full candidate list for the cases where you have not found that anchor yet.
Why the MX check matters
Before guessing a single address, confirm the domain can receive mail. If a domain has no MX records, no address on it will work, no matter how well you guess the pattern. Companies often use a different domain for email than for their website, for example a shorter brand domain, so a missing MX is a hint to search for the right one.
acme.com MX 10 aspmx.l.google.com accepts mail
acme-group.com MX (none) website only, try another domainWhen the MX points to Google Workspace or Microsoft 365, the address format is usually consistent across the company, which makes pattern inference reliable. Catch-all domains, which accept every address, will make any verifier say valid; treat those results with care.
From guess to verified address
- Generate the list here and remove formats the company obviously does not use.
- Run the candidates through the email address checker for syntax, typos and MX confirmation.
- Use a verification service that performs SMTP checks to confirm which mailbox exists.
- Never send to unverified guesses. Each bounce lowers the reputation of your sending domain and mailbox.
A bounce rate that climbs past a few percent is enough for Google and Microsoft to start filtering an entire domain. Protecting that reputation is the reason InboxOne separates outreach domains from your main company domain and rotates mailboxes across them: a bad list hurts one sending domain, not your brand.
