Port 143: IMAP
Mailbox access, unencrypted or upgraded with STARTTLS. Prefer IMAPS on 993.
- Free
- No Sign-Up
- Runs in Your Browser
Port Lookup
Port 143 at a glance
Port143
ProtocolTCP
ServiceIMAP
Open to the Internet?Only to addresses that need it
See What Is Listeningss -lntup | grep ':143 '
Test From Outsidenc -zv your-server 143
Block with UFWufw deny 143/tcp
Block with nftablesnft add rule inet filter input tcp dport 143 drop
IMAP uses TCP port 143. Mailbox access, unencrypted or upgraded with STARTTLS.
Prefer IMAPS on 993.
Allow port 143 only from the addresses that need it: your office, a VPN or a bastion host. The firewall rule generator builds those rules for nftables, iptables and UFW.
Other Ports
20 FTP Data21 FTP22 SSH23 Telnet25 SMTP53 DNS67 DHCP Server80 HTTP110 POP3123 NTP143 IMAP161 SNMP389 LDAP443 HTTPS445 SMB465 SMTPS514 Syslog587 Mail Submission853 DNS over TLS993 IMAPS995 POP3S1194 OpenVPN1433 Microsoft SQL Server1900 SSDP / UPnP2049 NFS2083 cPanel (SSL)2087 WHM (SSL)3306 MySQL / MariaDB3389 RDP3478 STUN / TURN5060 SIP5432 PostgreSQL5900 VNC6379 Redis8006 Proxmox VE8080 HTTP Alternate8443 HTTPS Alternate11211 Memcached25565 Minecraft27017 MongoDB51820 WireGuard
Questions
What is port 143 used for?
IMAP. Mailbox access, unencrypted or upgraded with STARTTLS.
Is it safe to open port 143?
Only to addresses that need it. Prefer IMAPS on 993.
How do I check if port 143 is open?
On the server, ss -lntup | grep ':143 ' shows what is listening. From another machine, nc -zv your-server 143 shows whether the firewall lets it through.
How do I block port 143?
With UFW: ufw deny 143/tcp. With nftables, add a drop rule for dport 143 in your input chain.
Free Tools
More tools
Port LookupWhat runs on a TCP or UDP port, and whether it should be open.Firewall Rule GeneratorGenerate iptables, nftables and UFW rules for common server set-ups.What Is My IPYour public IP address, reverse DNS, network and ASN.IP Reputation CheckerCheck an IP against spam blocklists and threat feeds at once.
Abuse from open ports on your VMs?
Frabs spots amplification, scans and floods leaving any VM and stops them, without touching your firewall.