Tools / Port checker / 143
Is port 143 open?
Port 143 is IMAP. Enter your server below to test it from Dallas, Amsterdam and London.
What port 143 is used for
Internet Message Access Protocol: mail clients read and sync mail that stays on the server.
Should port 143 be open?
Open it only to the addresses that need it. Require STARTTLS, or use IMAPS on port 993 and close 143.
How to open port 143
Ubuntu or Debian with ufw, allowing only your own address (replace 203.0.113.10):
sudo ufw allow from 203.0.113.10 to any port 143 proto tcp
Rocky, Alma or CentOS with firewalld:
sudo firewall-cmd --permanent --add-port=143/tcp && sudo firewall-cmd --reload
Windows Server, in PowerShell as administrator:
New-NetFirewallRule -DisplayName "Port 143" -Direction Inbound -Protocol TCP -LocalPort 143 -Action Allow
Then check that the service listens on all addresses, not only 127.0.0.1, and test again above.
Check another port
21 FTP22 SSH23 Telnet53 DNS80 HTTP110 POP3443 HTTPS993 IMAPS995 POP3S1433 Microsoft SQL Server2083 cPanel2087 WHM2375 Docker API3000 Development servers3306 MySQL / MariaDB3389 RDP5432 PostgreSQL5900 VNC6379 Redis6443 Kubernetes API8000 Alternative HTTP8080 Alternative HTTP8443 Alternative HTTPS9000 Portainer9090 Prometheus9200 Elasticsearch10000 Webmin25565 Minecraft27015 Steam / Source game servers27017 MongoDB
Run your service on a PrivateByte server: a firewall you control and every port yours to open.