How to verify a laposte.net email address

The reply that matters is the one to RCPT TO, the step where the checking server names the recipient. La Poste answered our made-up laposte.net address with 550 5.1.1 Recipient address rejected: User unknown. Adresse destinataire invalide. Invalid recipient. LPN007_416. A 5xx code at that step is a permanent "no such mailbox", which is the same answer a real message would get, so SimpleVerifier marks the address invalid with the reason "Mailbox not found". A 250 at the same step means the mailbox exists and comes back valid.

Before trusting a "valid", a careful verifier also offers a random address that cannot exist. La Poste rejected ours, so laposte.net is not a catch-all: a 250 for your address is a real signal. Temporary 4xx replies (421, 450, 451) are about the connection, not the mailbox, and come back risky with "Server would not confirm" rather than invalid. Hard bounce vs soft bounce explains why that split matters.

Because La Poste answers honestly, laposte.net is one of the domains where verification removes bounces before they happen. Drop the invalid results, keep the valid ones, and re-check the risky ones later: a temporary reply on one day often turns into a clear answer the next.

A valid result only means the mailbox exists today. Addresses on an old consumer list go stale as people stop using them, so re-verify before each large send to an aged segment; how often to verify an email list gives a schedule. Upload the CSV to the verifier and download the valid, risky and invalid rows as separate files.