Port 587 — SMTP submission
Quick reference for TCP/UDP port 587, used by SMTP submission. Includes what the service does, security guidance and related ports.
What is port 587?
Mail submission with STARTTLS — preferred over port 25 for clients.
What port does SMTP submission use?
SMTP submission listens on port 587 by default.
Security guidance
Low risk — designed for public exposure
Port 587 (SMTP submission) is designed for public exposure. Standard hardening (TLS certs, current firmware, sensible rate limits) is enough — no special isolation needed.
Related ports
Frequently asked
What is port 587 used for?+
Port 587 is the standard TCP/UDP port for SMTP submission. Mail submission with STARTTLS — preferred over port 25 for clients.
What port does SMTP submission use?+
SMTP submission listens on port 587 by default.
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