An IP address identifies a computer.

[mouakter13]

As we've said, SMTP is the standard protocol for transmitting email on the web. It's what mail servers use to send and receive email on the Internet.

For example, when you send an email, your email client needs a way to upload the email to the outgoing mail server. The outgoing mail server then needs a way to transfer your email to the recipient's incoming mail server.

Mail servers are a lot like website servers in that while there may be a user-friendly front-end domain name , the actual communication happens via IP addresses, such as 222.501.285.45 (for more on how this happens, read our introduction to the Domain Name System, or DNS ).

A "port" is another way to help computers ( such as two mail servers ) communicate with each other:

A port identifies a specific application/service running on that finland phone number data computer, such as SMTP.
Here's an analogy to make it a little more human-friendly:

An IP address is the physical address of a business complex. A port is the number of a specific business in that business complex.

If you want to deliver something to that business, you can't just direct it to the business complex, you also need a way to make sure it gets to the right place within the business complex.

The IANA , the organization responsible for assigning IP addresses worldwide and other tasks, is also responsible for registering port numbers for common Internet services, including SMTP.

Why does your SMTP port matter?
If you want to connect to an SMTP server (such as Gmail's SMTP server ), you need to enter its IP address and port number.

However, there are multiple common SMTP ports (more on this below) and not all of them work in all situations.

For example, port 25, the standard SMTP port for moving messages between mail servers, is often blocked by ISPs and cloud providers (including Google Cloud Platform, which is what Kinsta uses).

Therefore, if you try to connect to an SMTP server via port 25, you will often run into problems because many services block port 25.