421: too many connections from your Free line
Free's outgoing mail servers refused the connection because too many were opened from your Free internet connection, at once or in a short period.
- Free
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 421
- Provider
- Free (free.fr)
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
421 too many connections
What it means
This reply comes from the servers Free subscribers send through, not from free.fr inboxes. Free gives two situations: several simultaneous connections from your line, which should only happen now and then, or too many connections opened from it, which earns a temporary ban of a few hours. The limit exists to keep a few compromised computers from clogging the servers with spam. Heavy but legitimate use, such as a mailing, can trigger it too, although the quotas cover personal use. If it keeps happening, something on your network is sending mail.
Common causes
- A mail program keeps retrying messages the server already rejected.
- A computer on your network is infected and sends spam.
- Someone uses an open or weak Wi-Fi network to send through your line.
- A mailing sent from your line exceeds the quotas.
How to fix it
- 01Check the outbox of every mail program on your network for messages stuck in a retry loop.
- 02Scan the computers on your network for malware.
- 03Secure your Wi-Fi with a strong password.
- 04Do not unblock the SMTP port on your Free router: Free advises against it, since a compromised device could then send spam directly from your line.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- postmaster.free.fr (Free)postmaster.free.fr
Related codes
- 421Too many recipients or mails from your Free line.Free's outgoing servers counted too many recipients or too many mails from your internet connection and stopped accepting more for now.
- 421Service not available.The receiving server is closing the connection and will not take mail right now. The reply is temporary, so the sending server keeps the message and tries again later.
421 at other providers
- 421 [RP-001]Outlook.com rate limit for the sending IP.Outlook.com is limiting how fast your IP can send to it because of the IP or domain's reputation; it is temporary and your server should retry.
- 421 [RP-002]Outlook.com rate limit on this connection.Your IP has sent more over a single connection than Outlook.com allows, a limit Microsoft ties to IP and domain reputation.
- 421 [RP-003]Outlook.com connection limit.Your IP has opened more connections to Outlook.com than it is allowed, a limit Microsoft links to IP and domain reputation.
- 421Temporary error or deferral.Yahoo or AOL refused your message for now with a 421, one of its two temporary error codes. Your server should keep it and retry; repeated deferrals point to reputation or complaints.
- 421Try again later.Xfinity turned the message away for now with a generic 421. Treat it as temporary and let your server retry: Xfinity uses it for several reasons it does not spell out.
- 421Reverse DNS lookup failed.Xfinity could not complete a reverse DNS lookup for your sending IP. It treats this as temporary, so your server should retry, but a broken DNS setup keeps it failing.