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Hey everyone and welcome back. Now in the previous nugget we had laid out our plans for this

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skill and we decided that the very first thing that we're going to talk about and tackle

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is this email server configuration. Now before we actually begin the actual configuration

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itself what we're going to do is talk about some of the key components at play here with

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respect to email. Now one thing we must know is that email is largely or should I say critically

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dependent on something called SMTP. This is the simple mail transfer protocol. Now this

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runs over port 25 by default so if you happen to have some type of firewall in play be aware

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that if you block this port you could be blocking your email services. Now with respect to SMTP

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this is what actually enables how email can be sent and how email can be stored. Now with

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respect to email there are some particular components to this architecture that we really

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have to be aware of. The first one is called the MUA. Now this stands for the mail user

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agents and this will basically be a particular program that we can use as a client to actually

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create our own email messages. Now there are many different MUAs available in the Linux world. One

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we will get to look at later on within this skill is the Thunderbird client. This is very well

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known within the world of Linux. Another very important component is the MTA. Now with respect

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to the MTA what this is going to do is going to actually take in the messages from the MUA,

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the mail user agent and once it has ingested these messages it's going to send it over to the

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corresponding mail server that is the target. Now there are different MTAs. One that we're going

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to be looking at in this skill right here. In fact very shortly within this nugget is one called

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Postfix. So really think about it. The MUA can talk to an MTA which is a server and that can pass

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on messages to another MTA. And the last component is the MDA. This is the mail delivery agent. So

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what this is going to do is it's going to take the information stored on the MTA and transfer it

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to the local mail spool. So really I can just draw this. We could have an MUA sending a message

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to an MTA server which then fires that off to the relevant MTA server based on a particular

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destination whatever it may be and the recipient user they could have an MDA which would actually

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pull that message in from this MTA. Now one thing to note with respect to email we have these

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different protocols. We have the POP3 protocol and we have the IMAP protocol. Now the way the emails

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happen to be retrieved are dependent on the type of protocol we happen to use. Let's say for example

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that we had some type of email server and this is where all our emails were coming in and being

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stored. Now us here as a client just on a regular computer if we were using POP3 we would contact

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our email server using POP3 and we would actually download the contents of our email onto our local

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machine. Okay so think about it. The messages go to the email server. We contact the email using

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POP3 and we effectively get a local copy on our physical machine right here. This means that the

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server up here can or may delete those emails after we have downloaded them and save up the space

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on the email server. Now the reality is this is more of an older approach. Instead what more often

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happens now is we use IMAP. So think about it like this. We have the PC wanting to read the emails.

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The emails are stored on the email server. If we use IMAP we just simply consult the email server

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and we read the data directly from the server so we don't actually download the local copy to our

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machine. We read the data from the server and present it on our PC and this is how basically

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modern email works. Things like Gmail when you happen to grab your laptop and you log into your

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Gmail you're contacting the server and it's being displayed on your local machine but the emails

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aren't actually stored there. Instead they are still stored within the email server. That means

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that if you happen to grab another laptop and log in to your email account you can still read

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the same emails because they are still on the same server. They've not been transferred and

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locally downloaded onto a particular machine. Everything is handled by the central server.

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So these are the some of the main components with respect to email servers that we want to be

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aware of. So like I say we were talking about particular MTAs. The MTA we happened to mention

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was one called PostFix. Now PostFix just as an aside actually builds upon and is backwards

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compatible with the older implementation called Sendmail. Now Sendmail was the OG. This was the

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first main one on the scene that made a splash but it is notoriously complex and it is a little

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bit insecure. So PostFix seeks to address some of these problems and make the process a little bit

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more secure and a little bit simpler. So that is what we're going to be focusing on. So what I'm

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going to say is Sudo app to install PostFix as well as something called Mail Utils. So if I hit

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Y and Enter that should begin the installation. What I want to do here is to specify the type

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of configuration I want. I'm going to specify an internet site. Now the system mail name you can

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specify whatever it is you so wish. I'll just type in something like say ipv0-test.com and hit tab

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and OK. And PostFix should begin installation or complete installation should I say. Okay so let's

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go into the Etsy directory. I will do an LS. Now we should actually have a file called PostFix

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which we actually do or rather should I say a directory that should be. So we go into the

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directory and within here the main configuration file is one called main.cf. So really try to

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remember this location. Etsy PostFix main.cf. Let's go in and have a look at this file then. So we'll

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go in and say main.cf hit Enter. Now within here we're going to see a whole bunch of different

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information. We can see how we can configure our SMTP banner which will populate our host

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name using a variable value and the mail name. If we scroll on down we see a lot of information

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relating to encryption i.e. transport layer security but further down this is really where we

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want to be focusing on. So we can specify our host name which is system. In this case here if we

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scroll on up this is the value here that's going to be populated my host name. In my case it will

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be system. Scroll back down. We can see things such as the aliases. Now aliases are very very

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useful. What this means is that we can ultimately alias a particular user so that mail for that

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user can be redirected to another user. So a good example of this would be taking an alias or rather

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specifying an alias within this particular file that is the Etsy aliases file and we could map

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the root user to my local account of IPv0 for example. So if I wanted to check the emails that

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were sent to the root user without having to change accounts i.e. without having to log in as the root

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user I could actually just have any mail that is sent to the root user relayed to my local account

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and still read them. Now my destination here these are all the locations specified here. So what this

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means is that if the server happens to get any emails for any of the addresses that you see here

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the server is going to keep them and deliver it to the local user. So if I send a message to

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at localhost for example it will be for my local user here. Now one thing to note here is that we

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have this configuration for relay host this is left blank. I just want to have a word of warning

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that you probably and I should say strongly want to leave this as blank. The reason being is that

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this could potentially compromise your system and that your server could ultimately be targeted to

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really spam messages. So quite honestly if you do not know what you're doing with this I really

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really would leave this blank. So now that we know that our main configuration file is this one right

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here main.cf and we are aware of our aliases and destinations so on so forth. Let's begin doing some

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basic testing of our mail service. So what I'm going to do here is I'm just going to exit out

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and I will clear the screen. So let me show you how we can actually use this mail service if I just

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see mail and say dash s for the subject matter. So I will just give this the subject matter of

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hello world. Now realistically I could send this email out into the big bad world. So I actually

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have a little test account called johnredtestatoutlook.com. Now if my local settings were configured

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correctly I had a reputable domain name and not just ipv0 at system which looks kind of fishy.

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I could send this off like I say if I enter now cc I don't want to add anyone in. I would just say

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this is just some tests that will fail sad face. Now to end the message you might have to press

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ctrl d. In my case I actually have to press ctrl shift d and with that the mail will be sent off

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but the reality is given that my domain is a little bit dodgy this is going to fail it's going

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to be rejected by the outlook servers. If I happen to issue the command mail we can actually see here

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this is an undelivered mail returned to sender and a hit enter. Now do not despair like I say if

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my domain was configured correctly and I really had an ipv0.com address or whatever it may be

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then this configuration would work just fine but for the purposes of our little testing

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do not worry about that at all. What we're now going to do is to try to test an email

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by sending it to another account on this system. So what I will do is I will say mail dash s and

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I'll maybe say hey there admin that will be the subject matter and what I will do is I will target

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the root on the local host which is this machine right here. So if I hit enter cc I don't want to

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add anyone in and I'll just say hello mr. Root this is John. I will press control shift D. Now if I

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happen to hit the mail command here notice there is no mail for ipv0 that is because ipv0 was the

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sender of this mail and the recipient should be the root account. So what I'm going to do is I'm

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going to change into my super user which is now the root account. If I hit the mail command now

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see we actually do have a message for the root account and we can see the subject here is hey

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there admin we can see the sender was ipv0 if I hit enter we can actually see the contents of that

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message. Now if I wanted to hit enter again we can see there's no more messages and now if I just

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change back to ipv0 once again what I'm now going to do is I'm going to modify my aliases file remember

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we talked about that so I'll go into the etse directory and then aliases again remember this

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location very very important we can actually see here there already is an aliase configured meaning

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that if we happen to send a message to quote unquote postmaster it's actually going to be sent to

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the root account. To check this out if I just go back out here and I say mail s hey postmaster

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and I address it to the postmaster of localhost I'll just say hey p.m for postmaster control

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shift d if I say mail again no mail for ipv0 but if I go into my super user and I say mail now

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notice here we're in the root accounts for here and we have received the message that was directed

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to postmaster so postmaster has been relayed to the root account instead. Now check this out if I

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just say d to delete this and q to quit what I'm going to do here is I will go back into ipv0 and I

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will say sudo nano I'll go into the etse aliases once again and I'm going to add another piece of

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information I'm going to see the root account should go to ipv0 now think about this we actually have

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a chain going on right here if someone sends a message to postmaster it's going to be targeted

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for root however because it's now targeted for root root is now mapping to ipv0 so ultimately

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whenever someone sends a message to postmaster it's really going to go to ipv0 which is my local

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account check this out then okay very very important now that we have modified this aliases

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file it will not take effect just yet what I've got to do is issue this command sudo new aliases

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now this is very very important we have to understand that the etse aliases file will not

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be updated it will not take effect until this particular command is issued so if I hit enter now

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check this out like I say in our aliases we send to postmaster postmaster goes to root root goes to

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ipv0 so let's try this out then we will say mail s and we'll just say I love donuts and we'll send

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this to postmaster at localhost and the message will just be just letting you know I love donuts

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not sure why the postmaster would have to know this information but nevertheless let's go with it

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ctrl shift d now who do you think is going to get this message then let's first try the super

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user so we are now the root account let's see if the root account has this message the I love

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donuts message is not there so if I press q to quit spot I change into ipv0 or rather that should be

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substitute user ipv0 so I'm now ipv0 clear the screen I now say mail check this out it's only ipv0

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who got that message and I can hit enter and we can actually see the contents of the email right

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here so notice it was originally sent to postmaster which would have been relayed to the root but it

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didn't actually go into the root account the root account automatically just passed it on via the alias

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to ipv0 so really that is us for our basic introduction into using postfix so really we

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want to be remembering that it's a postfix main dot cf configuration file we also want to remember

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that we can create aliases in the etsy aliases file and if we want those changes to actually take

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place we must use the new aliases command but for now as we can see here we are reading our files

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we want to see a better way how we can actually manage our local mail service and well that's

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what we're talking about in the very next nugget so I hope this has been informative for you and

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I'd like to thank you for viewing