Port25— SMTP relay
TCP 25 sert au transfert de courrier SMTP, généralement entre serveurs de messagerie. Les clients doivent utiliser le point de soumission indiqué par leur fournisseur.
Registry assignments, software defaults and local listeners are different things. A port number alone does not identify or secure a service.
Configuration and troubleshooting
Distinguez la réception, le relais sortant et la soumission par les clients. Consultez les journaux de messagerie et les règles de sortie du fournisseur avant de conclure à un conflit de port local.
Important limitations
Ne configurez pas de relais ouvert. Un socket accessible ne renseigne ni sur la politique des destinataires ni sur la réussite de la livraison du courrier.
Read-only checks: run on the server host
Choose the commands for your OS. Check TCP and UDP separately. No result is not a lasting availability guarantee; inspect host and container separately.
Linux
sudo ss -ltnp 'sport = :25'macOS
sudo lsof -nP -iTCP:25 -sTCP:LISTENWindows PowerShell
Get-NetTCPConnection -LocalPort 25 -State ListenSources and review
Sources checked on:
This review covers the explanations and sources on this page, not your device or every community software entry below.
Logiciels utilisant ce port (4 logiciels)
Community software entries: links are references, not individual verification.
SMTP Mail
Simple Mail Transfer Protocol
Conseils d’utilisation
- Avant d’utiliser le port 25, vérifiez qu’il n’est pas occupé par d’autres services
- En cas de conflit de ports, envisagez d’utiliser d’autres ports ou d’arrêter le service qui occupe le port
Questions fréquentes
What is port 25 used for?
Port 25 sits in the Email & Messaging category. This page lists the registered purpose and the software commonly associated with it; to see what is actually listening on a specific machine, check the process with ss/netstat.
Is port 25 TCP or UDP?
The registered protocol on this page is TCP. The same number behaves independently on each protocol: TCP may be listening while UDP is idle, so check them separately.
How do I check if port 25 is in use?
On Linux: sudo ss -tlnp 'sport = :25' for an exact port match. On macOS: sudo lsof -nP -iTCP:25 -sTCP:LISTEN. On Windows PowerShell: Get-NetTCPConnection -LocalPort 25 -State Listen. A listener counts as confirmed only when you can see the bind address and process name; without root/admin you will not see other users' processes.
Is port 25 secure? Should I open it in my firewall?
A port number has no inherent security — it depends on whether the listening service is correctly configured and whether it needs exposure at all. Keep loopback/internal-only services firewalled; where public access is required, pair it with source restrictions, VPN or authentication. The caution section on this page lists port-specific risks.
En bref
- Port
- 25
- Protocole
- TCP
- Catégories
- E-mail et messagerie
- État d’utilisation
- 4 logiciels utilisant ce port
Ports associés
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