IANA initially assigned port 465 for an encrypted version of SMTP called SMTPS. However, IANA ...
What about port 465? Interestingly, port 465 was never published as an official SMTP transmission or submission channel by the IETF. Instead, the Internet Assigned Numbers Authority (IANA), who maintains much of the core internet infrastructure, registered port 465 for SMTPS. The purpose was to establish a port for SMTP to operate using Secure Sockets Layer (SSL).
465. 2525. Port 25 is commonly used for SMTP relay, but you should not use it for SMTP submission because most providers block it. If you want to configure your WordPress site or email client to use SMTP, you should start with port 587 as your first choice, as it’s the standard port for SMTP submission.
SMTP Port 465. SMTP port was the first secure and encrypted email submission port which is using SMTP over SSL methodology. After some time with the emerge of the Port 587 SMTP port 465 is deprecated officially and provided for use of other protocols. But today many ISP and cloud hosting providers support and provide port 465 for SMTP submission.
Today, port 465 is still listed on the IANA registry as the service port for message submission and URL Rendezvous Directory for SSM, URD for short. However, both of these services listed for port 465 adds to the confusion around the port, because URD has nothing to do with SMTP. Port 587: Message submission. Tl;dr Port 587 is the default port for SMTP message submission. Port 587 has always been the default port for message submission.
Port 465. Almost every ESP does not accept connections on port 465. Port 465 was never published by the Internet Engineering Task Force (IETF) as an official SMTP transmission channel but was registered as an SMTP port by the Internet Assigned Numbers Authority (IANA).
Port 465: Deprecated and out-of-date SMTP port. Port 465 is no longer an accepted standard for SMTP. However, there are some legacy systems that still use port 465 for SMTP, and some help pages on the internet still suggest port 465 as the recommended setup. Our advice? Don’t do it unless your application absolutely requires it.
SMTP protocol: smtps (port 465) v. msa (port 587) Ports 465 and 587 are intended for email client to email server communication - sending outemail using SMTP protocol. Port 465is for smtps. SSL encryption is started automatically before any SMTP level communication. Port 587is for msa.