- [Instructor] Servers Part 2: E-mail and Proxy Servers.
An e-mail server stores and supplies
incoming and outgoing e-mail to users
and possibly to other e-mail servers.
Common usages include POP3 accounts, IMAP accounts,
and HTTPS connections within a web browser.
An e-mail server might handle the sending of data,
the receiving of data, or both.
For the A-plus exams,
you should know how to connect a client to an e-mail server.
This is done by using appropriate e-mail client software
such as Outlook,
and knowing the server name,
protocols, and ports to be used,
the username and password,
and whether there is any additional security involved.
One common example
of an e-mail server is Microsoft Exchange,
so very common to have that with a Windows server.
And so if we look here,
we have our LAN and we have our client computers,
and we have two e-mail servers,
one here which is located in the DMZ area
on this side of the firewall,
and one over here that's just on the internet,
out on the cloud.
And you might have either of these
in your company or organization,
and there's different reasons for these.
You might wanna have your e-mail server internally
for various reasons.
And if you did,
you'd wanna protect that to a certain extent
by placing it on a DMZ.
You don't want it on the LAN.
This way, clients on the LAN can access the e-mail server,
but those clients on the LAN are protected by the firewall.
Also clients out on the cloud, out on the internet,
can access the e-mail server as well if necessary.
People working from home, people on the road.
Or the e-mail server could be stored on the internet,
on the cloud altogether,
and people access it from wherever they are.
At the workplace, at home, on the road, and so on.
And so you configure
the client computer's software like Outlook
or whatever it is that you're using to connect out
to the e-mail server.
And so let's say we were just configuring a POP3 account.
We'd have to set that up here,
and we would need to know the e-mail server's name,
for example, mail.example.com,
and we need to know that mail server name
for POP3 and also for SMTP.
Then we'd need to know the port numbers
that those protocols are using.
So for example, for secure POP3, that would be 995.
For secure SMTP, that would be 465.
And then the username and password,
and then we'd be able to connect through to get our e-mail
over the internet or through the LAN to our DMZ,
wherever that e-mail server is stored.
Now, a proxy server is used primarily as a go between
for the client and the website accessed.
It's commonly used to cached information
so that another user accessing the same webpage
won't have to get it from the internet
because it already exists on the proxy server,
which increases general performance and efficiency.
Most commonly, it's used with HTTP and HTTPS,
but it could be used by other protocols as well,
such as FTP and also SMTP with e-mail servers.
Examples of this include Squid,
also Apache web server with the appropriate proxy add-on,
WinGate and the proxy role in Windows Server.
So you could use a Windows server for that as well.
So let's show how this works.
Here, we have some computers on the local area network,
and we have a proxy server here as well.
So let's say that one of these computers
wanted to go to a website,
and we'll just use example.com as the example.
That computer would go through the proxy server every time
and then out to the internet and out to that website.
That web information, that website page,
would be stored at the proxy server
and then forwarded to this client.
Later, if another computer
wanted to go to that same web server,
it wouldn't actually have to go out to the internet
to get that homepage information
because that is stored at the proxy server.
So that information would be forwarded
by the proxy server to this client,
and it'll effectively be faster
and more efficient because of that.
Now, on the client side,
first of all you have to have the server set up to do this,
but you'd have to make the connections
from the client side as well.
So to do that in Windows,
you would go to your Internet Properties,
which you can get to from the browser
or from the Control Panel.
You would go to Connections,
then you'd go to LAN settings,
and then you would select Proxy server.
"Use a proxy server for your LAN."
And that's for this individual client.
Then you'd need to know the IP address of that proxy server,
or the name, so that you could connect.
And you'd type in the IP address
and the ports you wanna use with that proxy server.
If we click on Advanced,
we'll see we have multiple options here.
We could do HTTP, which is normally port 80.
Secure, meaning SSL or TLS, which is normally port 443.
FTP and so on.
Again, you just need to know the name
or the IP address of that proxy server
and the ports that it is using
internally on the inbound side to allow those connections.
Once that's done,
that connectivity could be made from this computer
through the proxy server,
and you would set that up on each of the clients.
Now, proxy can also be used in reverse.
To protect a web server,
an organization might implement a reverse proxy.
This device is placed within the area of the network
where that web server resides.
Requests from clients on the internet
are forwarded by the reverse proxy to the web server.
This way, the clients are unaware
of the web server's actual identity.
Reverse proxies can also be used
for encrypting the web session through the internet
and also load balancing
where client requests can be distributed
to multiple web servers.
Let's say we had a very busy website.
We might have three web servers
that are mirrors of the same website.
The reverse proxy would select the web server
that's being used the least at the current time,
so it balances the load between web servers,
especially when there's a lot of traffic
over the internet to that website.
Now, remember, the A-plus exams
don't require in-depth knowledge of servers,
but make sure that you know the basics
when it comes to e-mail servers and proxy servers
and their locations on the network.