Before you guess someone’s email address

You know someone's name and employer. The company appears to use first.last@, so you try the same pattern and run a check. It comes back valid.

You have evidence that the server may accept mail for that address. You haven't established that it reaches the person you named. There may be another employee with the same name, an old alias, or a catch-all configuration accepting every guess.

The uncertainty matters if you're about to send a proposal, an invoice or anything intended for one person. A successful delivery to the wrong inbox is still a mistake.

For an existing customer, use a known channel to ask for the right contact address. If a company publishes an address for your particular enquiry, follow that route. Don't silently replace a bounced customer address with one inferred from a naming pattern.

And keep outreach decisions separate from technical checks. An address that can receive mail hasn't thereby requested your message.