What is Email permutation?
Email permutation is generating likely addresses for a person by combining their name with a company domain in common patterns, such as first.last@ or flast@.
Also called: email pattern guessing, dictionary attack.
Given Jane Smith at example.com, a permutation list would include jane@, jane.smith@, jsmith@, janes@ and so on. Some tools then check each guess with SMTP verification and keep whichever the server accepts. On a catch-all domain every guess is accepted, so the method cannot tell which one is real.
There is a legal dimension in the US. CAN-SPAM section 7704(b)(1) makes it an aggravated violation to send, or to assist by providing addresses for, an unlawful commercial email where the addresses were generated by combining names, letters or numbers into numerous permutations. It adds to a violation that already exists rather than standing alone, but it is the route by which a list supplier becomes a co-violator.
For your own one-off research, a permutator is a reasonable way to work out a colleague's or a known contact's format. For building lists, an address the business published itself is both more reliable and on firmer ground.
67Leads does not generate emails by pattern: addresses are read from each company's own website. The email permutator exists for the one-off case and explains the limits.