Email

Port 587

SMTP-Submission

Authenticated email submission from client to mail server (STARTTLS)

Port
587
Protocol
TCP
Service
SMTP-Submission
Security
Safe
Full name: SMTP Message Submission

What is port 587?

Port 587 is the official (RFC 6409) SMTP submission port for email clients (Thunderbird, Outlook, mobile apps) to send outgoing mail to their mail server. It uses STARTTLS to upgrade the connection to TLS encryption. Unlike port 25 (server-to-server relay), port 587 requires authentication. ISPs do not block port 587 the way they block port 25. It is the recommended submission port alongside port 465.

Related ports

Port 25 SMTP Email transmission between mail servers
Port 465 SMTPS Encrypted email submission via implicit TLS (SMTPS)
Port 143 IMAP Server-side email management without encryption (IMAP)
Port 993 IMAPS Encrypted IMAP email access over TLS (IMAPS)
← All ports