# ProtocolLab HQ

HTTP codes Ports

TCP Port

25 SMTP

Simple Mail Transfer Protocol — server-to-server email relay. Often blocked by ISPs to curb spam.

Protocol: TCP · Port: 25

ProtocolLab HQ — HTTP codes and ports, looked up fast.

A quick developer reference for HTTP status codes and common network ports, compiled from the relevant RFCs and IANA registries. Port assignments and status semantics occasionally change; check the current standard when it matters.