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Port 587: SMTP Submission (STARTTLS)

Port 587 is the official standard port for email message submission by mail user agents (MUAs) using STARTTLS.

Protocol
TCP
Category
Email Submission
Common Services
Postfix, Exim, Haraka

What is Port 587 and How Does It Work?

Port 587 is the official standard port for email message submission by mail user agents (MUAs) using STARTTLS.

Security Vulnerabilities & Attack Vectors on Port 587

Strict authentication and rate limits prevent spammers from abusing outbound mail services.

Auditing & Scanning Port 587 with Nmap

Run the following command to check if Port 587 is reachable and determine service fingerprints:

nmap -p 587 --script smtp-commands

Frequently Asked Questions

How do I check if Port 587 is open?
Use cyber-tool.org diagnostic tools or run 'nc -zv 587' in your terminal to verify open socket connections.
Is it safe to leave Port 587 open to the internet?
Exposing Port 587 (SMTP Submission (STARTTLS)) publicly introduces potential exposure. Protect it with IP whitelisting, firewalls, and encryption.