Well-known · Cross-platform

143 IMAP

TCP Yes
UDP Assigned
SCTP
DCCP

What it is

Internet Message Access Protocol for server-side mailbox access (cleartext).

When / why

Prefer IMAPS (993). Allow only with STARTTLS enforced.

Protocol status detail

TransportStatusMeaning
TCP Yes Assigned by IANA and standardized, specified, or widely used on this port.
UDP Assigned Assigned by IANA, but not standardized, specified, or widely used on this port.
SCTP Not applicable for this transport.
DCCP Not applicable for this transport.

Port range

Well-known (0–1023). System port for a core service. On Unix-like systems, binding it requires superuser privileges.

Browse all ports →

Firewall rules for port 143

Copy-ready inbound rules for the active transports. Replace every <source> placeholder with the specific host, subnet, or CIDR that should reach this port.

⚠ Unencrypted or unauthenticated by default — prefer a TLS variant or tunnel over VPN/SSH rather than exposing this port directly.

ufw

sudo ufw allow proto tcp from <source> to any port 143

Allow TCP 143 (IMAP). Replace <source> with the network/host that should reach it.

firewalld

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="143" protocol="tcp" accept'

Allow TCP 143 (IMAP) from <source>. Run 'firewall-cmd --reload' afterwards.

nftables

nft add rule inet filter input ip saddr <source> tcp dport 143 accept

Allow TCP 143 (IMAP). Assumes table 'inet filter' with an 'input' chain.

iptables

sudo iptables -A INPUT -p tcp -s <source> --dport 143 -j ACCEPT

Allow TCP 143 (IMAP). Persist with iptables-save/netfilter-persistent.

Azure NSG

az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-imap-143 --priority 1000 --access Allow --direction Inbound --protocol TCP --source-address-prefixes <source> --destination-port-ranges 143

Inbound rule for 143 (IMAP). Set <source> to a CIDR; lower priority number = higher precedence.

AWS Security Group

aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=tcp,FromPort=143,ToPort=143,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound TCP 143 (IMAP). Replace <source-cidr> (e.g. 10.0.0.0/16).

GCP firewall

gcloud compute firewall-rules create allow-imap-143 --direction=INGRESS --action=ALLOW --rules=tcp:143 --source-ranges=<source-cidr> --network=<network>

Ingress rule for 143 (IMAP). Scope with --source-ranges and optionally --target-tags.

Windows netsh

netsh advfirewall firewall add rule name="Allow IMAP 143/TCP" dir=in action=allow protocol=TCP localport=143 remoteip=<source>

Inbound TCP 143 (IMAP). Set remoteip to a host/subnet; 'any' is discouraged.

Windows PowerShell

New-NetFirewallRule -DisplayName "Allow IMAP 143/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 143 -RemoteAddress <source>

Inbound TCP 143 (IMAP). Replace <source> with a host or subnet.

Rules are generated only for transports marked active for this port. They default to an inbound allow with an explicit source placeholder — never any. Review direction, scope, and rule precedence before applying in production.