What port does SMTP use?

[mouakter13]

Different ports for different purposes
Beyond the above implications, different SMTP ports also serve different purposes.

There are two major phases in SMTP transmission:

Send – Send an email message to an outgoing mail server. For example, when you send an email in Apple Mail, that message must be sent to the outgoing mail server.
Relay – the process of retransmitting the message between two servers. So after an email is “sent” to the outgoing mail server, the outgoing mail server “relays” that message to the recipient’s mail server.
If you’re setting up your email client or WordPress site, you’re most concerned about the “sending” part of the process.

While “relaying” is definitely an important part of SMTP, most people don’t need to set up their own email server.

On the modern web, there is no such thing as a single SMTP port. There are actually four common SMTP ports:

25
587
465
2525
Let's review them.

What is Port 25 used for?
Port 25 was established in 1982, making it the oldest SMTP port.

Port 25 is still known as the standard SMTP port and is finland phone number data primarily used for SMTP relaying .

However, if you are setting up your WordPress site or email client with SMTP, you typically don't want to use port 25 because most residential ISPs and cloud hosting providers block port 25.

Why? Because port 25 is commonly abused to send spam from compromised computers.

Remember: there is a difference between SMTP sending and SMTP relaying. So while port 25 is great for SMTP relaying, it is not a good choice for SMTP sending.

What is Port 587 used for?
Port 587 is the default port for SMTP submission on the modern web. While you can use other ports for submission (more on that below), you should always start with port 587 as the default and only use a different port if circumstances dictate (such as if your host blocks port 587 for some reason).