Verifying Free addresses

• Unknown recipients return a 550, so the answer is honest when it arrives.
• Connection throttling is severe by European standards and a large batch will take far longer than the same batch against Orange.
• The aliceadsl.fr domain came from an acquisition and routes into the same system.
• Free has a long-standing reluctance toward bulk senders and blocks at the connection level.

• Free has a reputation among French senders for hard blocking, and their tolerance for unrecognised bulk sources is low.
• The audience is technical relative to Orange's, which usually means quicker unsubscribes and fewer spam complaints.
• Segment French ISP addresses separately from French Gmail addresses; they behave nothing alike.

Here's the arithmetic with made-up but reasonable numbers. Say a provider tolerates one recipient check every three seconds from a single IP before it starts refusing connections. Your list has 3,000 free.fr addresses. At that pace the segment needs 9,000 seconds, which is two and a half hours, while 3,000 rows at a more relaxed provider might clear in a few minutes.

Push harder and you don't finish sooner. The server starts answering with temporary failures or drops the connection, and every row probed during the penalty comes back without a verdict. So when your results file shows the free.fr rows arriving last, that's the pacing doing its job. If a vendor promises a fixed turnaround for any list regardless of which providers are in it, ask what happens to the slow rows when the clock runs out.

There are only three honest outcomes for a row the server wouldn't discuss in time: keep waiting, retry later, or return it as unknown. The dishonest outcome is a guess dressed up as a result. Some tools mark leftover rows valid so the list looks clean, and some mark them invalid so the tool looks strict. You can test which one you're dealing with. Put a free.fr address you know is real, such as a colleague's, into a large batch and see what comes back.

For reference, free.fr and aliceadsl.fr both answered on mx1.free.fr and mx2.free.fr in our lookup on September 19, 2026, so rows on either domain draw on the same allowance. We return unresolved rows as unknown with the throttle named, and they aren't billed. Resubmitting them the next morning is usually the cheapest fix available.