Well-known · Cross-platform

587 SMTP submission

TCP Yes
UDP Assigned
SCTP
DCCP

What it is

Authenticated mail submission, historically with STARTTLS.

When / why

Client mail submission. RFC 8314 now prefers implicit TLS on 465.

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 587

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

ufw

sudo ufw allow proto tcp from <source> to any port 587

Allow TCP 587 (SMTP submission). 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="587" protocol="tcp" accept'

Allow TCP 587 (SMTP submission) from <source>. Run 'firewall-cmd --reload' afterwards.

nftables

nft add rule inet filter input ip saddr <source> tcp dport 587 accept

Allow TCP 587 (SMTP submission). Assumes table 'inet filter' with an 'input' chain.

iptables

sudo iptables -A INPUT -p tcp -s <source> --dport 587 -j ACCEPT

Allow TCP 587 (SMTP submission). Persist with iptables-save/netfilter-persistent.

Azure NSG

az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-smtpsubmission-587 --priority 1000 --access Allow --direction Inbound --protocol TCP --source-address-prefixes <source> --destination-port-ranges 587

Inbound rule for 587 (SMTP submission). 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=587,ToPort=587,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound TCP 587 (SMTP submission). Replace <source-cidr> (e.g. 10.0.0.0/16).

GCP firewall

gcloud compute firewall-rules create allow-smtpsubmission-587 --direction=INGRESS --action=ALLOW --rules=tcp:587 --source-ranges=<source-cidr> --network=<network>

Ingress rule for 587 (SMTP submission). Scope with --source-ranges and optionally --target-tags.

Windows netsh

netsh advfirewall firewall add rule name="Allow SMTP submission 587/TCP" dir=in action=allow protocol=TCP localport=587 remoteip=<source>

Inbound TCP 587 (SMTP submission). Set remoteip to a host/subnet; 'any' is discouraged.

Windows PowerShell

New-NetFirewallRule -DisplayName "Allow SMTP submission 587/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 587 -RemoteAddress <source>

Inbound TCP 587 (SMTP submission). 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.