Port 587 is a very popular port number that is used for SMTP. The SMTP or
Simple Mail Transfer Protocol is used to transfer mail messages between mail servers. Actually, the SMTP uses port 25 by default. But as the emails are abused a lot the port 25 is generally restricted in different scenarios. The alternative port number is 587.
Port 587 Features
The modern web email implementations use the TCP or Port 587 for email submission. What makes Port 587 very powerful is the ability to support encryption to make email transmission more secure. The port 587 supports the
TLS encryption support.
TLS (Encryption) Support
Port 587 is defined in the
RFC 2476 . Below are the steps for creating a TLS connection with port 587. The openssl can be used to make a TLS connection to port 587. The TLS connection to port 587 is accomplished with the
-starttls option .