Instructor: In this lesson,
we're going to talk about email servers.
Now when it comes to email servers, these are servers
that are set up to be able to help us compose a message
and send it to another user,
on either our own network or across the internet
to any other network in the world.
Now as a technician, there are really four main types
of servers that you're going to come across.
These include SMTP,
or Simple Mail Transfer Protocol servers,
Post Office Protocol 3, or POP3 servers,
Internet Message Access Protocol, or IMAP servers,
and Microsoft Exchange Servers, simply known as Exchange.
Now when it comes to SMTP,
this is what we call the Simple Mail Transfer Protocol.
And this is a protocol that specifies
how email should be delivered
from one mail domain to another.
So if I send an email from support@diontraining.com
to your Gmail account,
it has to go through my SMTP server,
and that message is then sent over to Google servers
to process and then deliver to you.
Now when we deal with SMTP servers,
the sender has to discover the IP address
of the recipient SMTP server,
and it does this by using the domain name
as part of the recipient's email address.
For example, if I know that I'm sending it
to you@gmail.com, I'm going to look up gmail.com
and get their IP address,
and my server is going to send my email
to that server's IP address using the SMTP protocol.
Now, once it gets there,
they're then going to look at what is in front of the @ sign,
in this case, you@gmail.com,
and they'll then find You and put it in the You mailbox,
which then you'll be able to access
the next time you log into Gmail to get your email.
Now, SMTP does stand for the Simple Mail Transfer Protocol,
but to keep things straight in my head, I always
like to think about it as this send mail transfer protocol.
Because when I think about SMTP,
I'm thinking about sending emails,
'cause that's everything that SMTP is used for.
When you use SMTP, it's going to operate over port 25
and be able to send messages from one SMTP server
to another using that protocol,
and that way it can send it out
to another message transfer agent known as an MTA.
The second type we have is what's known as POP3,
or Post Office Protocol version three.
Now the Post Office Protocol, or POP,
is really an older email protocol
that has been around for a very long time.
I had my first POP3 account back in the 1980s,
it's that old.
Now when you're using Post Office Protocol version three
as your protocol, you're going to be doing this over port 110.
When you use POP3, you're going to be able to connect
to your email server, download your messages
and then process them on your local machine.
Now this is a big deal when you're dealing with POP3
and you have multiple different devices
that are accessing the same account,
because every time you connect,
it's typically by default going to be set up
to download your messages and delete them from the server.
So for example, if you're using a Gmail account
but you're using Thunderbird, or Apple Mail,
or Microsoft Outlook to be able to access
that POP3 server and you're using the POP3 protocol
to get your mail from Gmail, it's going to download those
to your computer and then delete them from the Gmail server.
Now, again, like I said, Post Office Protocol
was developed all the way back in the 80s,
and back then most people had a single computer
that they accessed their email from,
so this wasn't a big deal.
But in modern times, that actually is a huge limitation
because if you're like most people,
you might have a desktop computer at work,
you have a laptop at home, you have a smartphone,
you have a tablet and all of these devices
are all checking your email.
And so if you're using Post Office Protocol version three
and you're downloading email to each of these devices,
some of your email is on some of these devices at all times
and it makes it very hard for you
to see all of your email at once.
So to overcome these limitations of POP3,
there is a new protocol developed, called IMAP,
and IMAP stands for the Internet Message Access Protocol.
Now IMAP is actually a mail retrieval protocol
that's designed to do mailbox management
when it goes to get your emails.
So in addition to be able to read your emails
and put them locally on your machine,
it can keep a copy on the server.
In addition to that, your email client
can actually manage the status of each of those messages
on that server every time it connects.
So if you're using IMAP as your protocol,
which operates over report 143,
you're actually going to be able to connect to that server,
receive your messages and read them.
And when you read them, it's going to mark it
on the server as being read.
So if I grab my iPhone and I read a message
and I then pull up my iPad,
the iPad will show that that message has already been read
because I've read it on my iPhone.
This is a great way to keep all of your devices in sync,
and it works really well when you're using services
like Yahoo, Gmail, and other email providers.
Now the fourth one we have is known
as Exchange or Microsoft Exchange.
And this is built by the Microsoft Corporation
and runs on Windows servers.
Now Microsoft Exchange is a mailbox server environment
designed specifically for Windows-based domain environments.
And it is still going to be operating
using a lot of the protocols we just talked about,
such as POP3 over port 110,
or IMAP, using port 143,
or SMTP, using port 25.
But all of this is done inside
of this exchange environment, using the exchange server.
Now, the reason I'm bringing this up as a separate item
in addition to the three servers we already talked about
of SMTP, POP3 and IMAP, is the fact that exchange
is widely used in many corporate environments.
And if you're working for a large organization
in the help desk or service desk,
you're likely going to be coming across Exchange
as one of the big things you're
going to be working with on a daily basis.
So I wanted to bring it up and make sure you're familiar
with the term Microsoft Exchange
and the fact that it is an email server
that's used by a lot of organizations around the world.