Online Mail Delivery: The Way It Works
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by: brianxavier
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To truly learn how any mailing system works, you need to be familiar with DNS, since your mail server utilizes this particular protocol to find out the right way to relay your e mail to its desired individual.
You probably already read about DNS , it is the protocol which converts domain names to ip addresses, these ip addresses give the true location of each and every computer on the net. One more, not as much familiar function of the DNS protocol, is that it is the system which tells your mail server exactly who is in charge of managing mail which belongs to some specific domain, the actual name that comes after the "@" inside your recipient's email.
Yet another concept that you should know is the SMTP standard protocol. SMTP is short for Simple Mail Transfer Protocol; it is the language underlying just about all e-mail communications. Typically you do not interact with the SMTP standard protocol directly, on the other hand the e mail client uses this protocol to be able to communicate with your outgoing mail server, and your outgoing mail server as well makes use of this specific standard protocol to communicate with your recipient's mail server.
The e-mail client in truth is simply a simple to operate software which makes use of SMTP along with other protocols so that you can send out and receive mail. POP3 is a second protocol utilized by your e-mail client; this protocol is in charge of downloading electronic mails from your mail server to your computer system. It's a highly straight forward protocol which simply just will provide the mail server with your username and password in order to authenticate you and after that begins fetching your e-mail.
Now you will be thinking, exactly how could the server differentiate between, SMTP transmission and pop3 transmission? To answer this subject, Let me begin by showing precisely how clients speak with servers online, it is really quite simple.
Each service has a specific channel, or port number, which is open at the server. As an illustration, pop3 utilizes port 110, both the email client as well as your outgoing mail server recognise that, so when your email client is attempting to retrieve email with the pop3 protocol, it utilizes that port number in order to speak with the server. In the same way if your mail client wants to use SMTP, it uses the port number associated with SMTP, which happens to be port 25.
This way, your server recognizes precisely which service you are requesting together with which standard protocol to utilize.
Now that you're familiar with these concepts, let's essentially observe the path of an email towards its destination.
Whenever you click on the send button, your mail client establishes a connection with your outgoing email server to the port connected with SMTP, which, as we already mentioned, is port 25 by default. Next it starts uploading your mail to your mail server.
As soon as your mail server finishes obtaining your email. It starts the process of essentially delivering it to the intended receiver. First, it breaks the email into 2 parts, the part before the "@" will be the username of the recipient, the part following the "@" is the domain.
At this point comes the part where it tries to search for the dns server permitted to tell you exactly which mail server is responsible for obtaining e-mails belonging to this domain. This is called the NS server. Your outgoing mail server achieves this through consulting a global dns database, a tree structure, each branch it consults in this tree, can be either the authorized dns server, or a branch that can get us nearer to the authorized dns server.
When the authorized dns server is located, the outgoing mail server sends a get query, asking it for the mail server in charge of obtaining mail on the domain included in the email. This kind of mail server referred to as the mx server or the mail exchange for that domain. Given that it finally found the mail exchange in charge of the domain name, it may well begin uploading our mail, specifying the username to give the e-mail to (the part before the "@")
Now your receiver can easily get connected to their pop3 mail server to access the email you sent to him. It might appear to be a long and even tedious process, however in reality it all takes place in a few seconds or even less.
About the Author
A number of ISPs lately started forbidding port 25 for users; this is certainly performed primarily to overcome junk e-mail and unsolicited email in general. To see whether your current ISP is actually blocking that port for everyone, How Can We Check If Port 25 Is Firewalled?.
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