How it works

Why one known address is worth fifty guesses

The email permutator produces every plausible address for a name and lets a verifier sort them out. That works, and it burns verification credits and a little goodwill with the catch-all domains it hits twelve times. When you already have one or two confirmed addresses at a company — from a signature, a LinkedIn contact, a reply, an old list — you do not need to guess. Companies choose a format once, at the point they set up their mail system, and almost never change it; the exceptions are acquisitions and very large organisations that ran out of unique first names. Learn the format from what you have, apply it to the names you need, and send only the result to the verifier.

The formats and how common they are

Across the B2B lists I work with, roughly half of companies use first.last. Another fifth use first alone — small companies, startups, agencies. flast (first initial plus last name) is the enterprise and legacy-Exchange favourite. firstlast, first_last and f.last cover most of the rest, and last.first or lastf show up in parts of Europe and Asia and in universities. The tool tests all of these plus hyphenated, reversed and initials-only forms, and it orders ties by that base rate so a single ambiguous sample still gets a sensible first guess.

When the samples disagree

Two formats at one domain usually mean one of three things. The company was acquired and kept the old staff's addresses. It grew past the point where first was unique and switched to first.last for new hires — in which case seniority predicts format. Or one of your samples is wrong: a personal alias, a shared mailbox, or a typo. The tool shows which sample matched which format so you can see the split rather than trust an average. When in doubt, use the format of the most recently hired person you can confirm.

Verify before you send

The right format gives you the address the person would have. Whether they still work there, whether the mailbox is full, whether the domain is a catch-all that accepts everything — those are questions for the email verifier, one address at a time, or the list-cleaning service at Rooster4am for a whole file. Generated addresses that fail verification are worth a second look at the name: a middle name in the source, a nickname, or a transliteration is the usual cause.

Frequently asked questions

Last reviewed September 16, 2026