I guess most of you might never wonder what actually happens to your mail when they are sending. So i am just providing a simple explanation to you about this topic.
Firstly let’s have a basic introduction to email:
Email was born in 1971 when a computer engineer beginning to use @ symbol to designate which computer should go to. It is a convenient and fast way to send your mails instead of wasting money on mail service and paper etc.
What happens to your email as soon as the send button is pressed?
The sender composes a message using the email client on their computer. When the user sends the message, the email text and attachments are uploaded to the SMTP (Simple Mail Transfer Protocol) server as outgoing mail. All outgoing messages wait in the outgoing mail queue while the SMTP server communicates with the DNS (Domain Name Server–like a phone book for domain names and server IP addresses) to find out where the recipient’s email server is located. If the SMTP server finds the recipient’s email server, it will transfer the message and attachments. If the recipient’s server can’t be found, the sender will get a “Mail Failure” notification in their inbox. The next time the recipient clicks “Send & Receive,” their email client will download all new messages from their own email server. You’ve got mail! -
We use an online email service like Gmail, Yahoo Mail or AOL to compose an email, add attachments and other data files. Also, we use email client software like thunderbird, outlook express, Outlook or MAC OS X’s Mail.
• When we send an email, our computer connects to our email service’s mail server. A server is a centralized computer which manages a specific type of service. An email server for instance, handles emails. The email server responsible for sending emails is called the SMTP (Simple Mail Transfer Protocol) server. One SMTP server can pass on the mail to another SMTP server and relay it to the destination through several hops.
• Every email has the sender’s address (e.g. email@example.com) and the recipient’s in the field (e.g. firstname.lastname@example.org). When an email is sent, the email client connects to the SMTP server of the sender’s email service (e.g. mailserver.sendermail.com). The client transmits the address of the sender, the address of the recipient and the content of the message.
• The SMTP server goes to work at locating the whereabouts of the recipient. Using the recipient’s mail ID (i.e. email@example.com) it locates the domain name – e.g.recipientmail.com.
• Note: If the recipient’s mail ID had the same domain name as the sender, then the process would be simpler. The SMTP server would have transferred the mail to its local outgoing mail server (POP3 or IMAP).
• Each domain name represents a unique Web address, called an Internet protocol (IP) address. Think of it as postal addresses of the internet. The link between domain names to their IP addresses is stored in the Domain Name Registry. The SMTP server then contacts the server where the registry is kept (The DNS Server). The DNS server sends back the address to the SMTP server.
• The SMTP server then proceeds to hand over the email to the SMTP server of the recipient’s email service (let’s call it mailserver.recipientmail.com). This SMTP server checks and confirms that the mail addressed to firstname.lastname@example.org belongs to it and hands it over to its counterpart “the POP3 server (or the IMAP server).
• Post Office Protocol (POP3) servers are the servers that do the job of receiving mails. The number “˜3′ is the version number of the protocol in use. POP3 servers have mail accounts (our email IDs). Each mail account is mapped to a username-password combination. Once the message is handed over to the POP3 server, it is kept and stored in the mail account till the recipient logs in and checks the mail.
• An email client connects to the POP3 server and tells it to allow download of the email. Once downloaded to the local machine, POP3 mailboxes do not retain a copy of the email. Thus, you cannot check your emails from another PC as it has already been downloaded. To nail this difficulty, IMAP was introduced. IMAP4 (Internet Message Access Protocol version 4) simply retains a copy of the emails on the server. This allows you to access your e-mail from any location with an internet connection.
How email is sent:
When someone, sends an email, it has to have an address in the form of email@example.com. The email gets sent by the client to an outgoing mail server via Simple Mail Transfer Protocol. The SMTP server is like your local post office, which checks your postage and address and figures out where to send your mail. It doesn’t understand domains, though. They’re a sort of abstract thing, so the SMTP server contacts a Domain Name System server. The DNS server is a sort of phone or address book for the internet; it translates domains to an IP address like “22.214.171.124.” Then, it finds out if that domain has any “MX” or mail exchange servers on it and makes a note of it. This is like your post office consulting maps of where your mail is supposed to go, calling their local post office, and checking to see if your friend has a mailbox or P.O. box to receive mail.
Now that the SMTP server has the proper info, the message gets sent from that server to the target domain’s mail exchange server. This server is referred to as an MTA, or Mail Transfer Agent. It decides where exactly to put the mail, much like how your friend’s post office figures out how best to get it delivered. Then, your friend goes and fetches the mail, usually using a client that works via POP or IMAP.
Pop and Imap:
These two acronyms plague email settings panels everywhere, so let’s take a deeper look at them. POP stands for Post Office Protocol. It’s useful because, like a post office, you can pop in, grab all of your mail, and then leave. You don’t need to stay connected, and aside from leaving a copy on the server, it’s a pretty cut-and-dry procedure. If you don’t leave a copy on the server, it doesn’t require much space or bandwidth either. You can use POP to grab mail from several different inboxes on several different email servers and consolidate them on one.
It has its drawbacks, though. POP is a unidirectional protocol; information travels one way. Once you download the email to a client, it’s up to the client to sort through its different statuses and so on. That’s fine if you only ever access mail from one place. Nowadays, though, it’s common to get email access from your phone’s client, the web interface when you’re away somewhere, and a client when you’re at home. It’d be tedious to sort through all of that info over several devices, assuming you’ve even kept a copy of each email on the server to begin with.
When you send an email message, your computer routes it to an SMTP server. The server looks at the e-mail address (similar to the address on an envelope), then forwards it to the recipient's mail server, where it's stored until the addressee retrieves it. You can send e-mail anywhere in the world to anyone who has an email address. In fact astronauts on the international space station use e-mail to keep in touch with their earth-bound colleagues’ yourself a me.
At one time, you could only send text messages without attachments via the Internet. With the advent of MIME, which stands for Multipurpose Internet Mail Extension, and other types of encoding schemes, such as UUencode, you can now send formatted documents, photos, audio and video files. Just make sure that the person to whom you send the attachment has the software capable of opening it.
Both SMTP and MTA:
Unlike your physical mailbox, your outgoing and incoming mails are handled by two different types of servers. There’s really no discrimination towards receiving servers; any computer can be made an MTA pretty easily and handle things well. Sending mail is a different story. SMTP servers must have static IP addresses, and most ISPs block port 25 so that their users can’t send mail themselves. Why? Because of the massive amounts of spam gnawing away at our collective bandwidth, the very stuff your MTA should be configured to filter out. You can configure your clients to use your ISP’s SMTP server in lieu of running your own. The point is that you need both an MTA and an SMTP server to use email, as each is specialized for what it does.
Some useful Information:
Your email program (the client) then sends the message off to an email server by using the Simple Message Transfer Protocol, or SMTP. The email server is basically a program running on another computer. For most people, the computer is located at your Internet service provider, or ISP.
At the server, the message is dissected and the recipients culled from the messages To, Cc and Bcc fields in the header. The SMTP server then finds the host computer for the recipients. For example, if the message is being sent to firstname.lastname@example.org, the server looks up microsoft.com and sends the message off to that computer.
For a few nanoseconds, the message hops around the Internet as it makes the connection to the destination computer.
At the destination computer, another SMTP server fetches the message and stuffs it into a mailbox for the intended user. There, it sits and waits until the user logs in to collect mail. But the mailbox on the server isn’t the same thing as the inbox in your PC’s mail program.
The recipient’s mail program collects new messages from his ISP’s server. The mail program uses the Post Office Protocol (POP) to fetch the message. POP is used instead of SMTP because the email message is no longer being sent on the Internet; it has arrived. All the POP does is fetch the message waiting on the server and transfer it back to the user’s computer and his email program.
After the mail messages are on the recipient’s computer, they’re stored in a database. Secretly, all email programs are database programs. After your messages are received, they exist in various mailboxes organized by your email program: Inbox, Deleted Items, and Junk, for example.
The email methods described here don’t apply to email systems at large organizations, such as Lotus Notes or Microsoft Exchange.
• In addition to POP is the Internet Message Access Protocol (IMAP)method of reading email. Unlike POP, IMAP doesn’t delete messages from the user’s mailbox on the server until the user deletes the message. Web-based email programs, such as Gmail and Hotmail, often prefer IMAP.
• Your email is stored on the ISP’s computer until you pick it up. Unless you retrieve those messages, your mailbox on the ISP’s mail server continues to fill up until it’s so bloated that no more messages can be received.
• Most ISPs limit the size of your mailbox. Additionally, your account may have size limits on individual messages, which often can’t be larger than 5 or 10 megabytes. Contact your ISP for specifics.
• When your mailbox gets full, the ISP bounces any new email you might receive. The message is returned to the sending SMTP computer, but the sender may not receive a notice that the message has bounced.
I know it would be good information to you. Thank you