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I know of domain name registrars, that you can use them to acquire your own domain name for a website; but, how do they connect to the internet and email (servers) globally?

I'm not exactly sure how to better word that.

Say I register example.com. What's actually going on here? Is there some master list of servers somewhere that your registrar updates, so that when people enter it into their browsers these servers will redirect your domain name to your website's server IP?

The main reason I ask this and am curious about it, as a programmer, is in regards to emails. How does myemail@example.com actually work? Who's in charge of managing that email, and what if someone else buys example.com 5 years from now? Could I host my own email address at home if I own a domain name, and would I want to do that?

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Quite a lot of questions but the main two ideas to have in mind:

  • the DNS is a hierarchy, or a tree: technically each node works exactly the same way, wherever it is in the tree; for a node to be resolved it has to be connected to some parent node; this is done in the DNS with NS records
  • domain name registrar play no operational role during resolution (except if they are also DNS provider, but this is orthogonal); they are only use to provision and update domain names at the parent zone (the registry)

Now for your questions:

Say I register example.com. What's actually going on here?

You go to a registrar. The registrar will check with the registry is the domain is available. Then it will collect data and money from you and then send the name desired and data (contacts, etc.) to the relevant registry typically using EPP as protocol. The registry will then update its authoritative nameservers to add NS records for your domain to point to the nameservers of your choice, so that the whole resolution works.

Is there some master list of servers somewhere that your registrar updates,

No, because the DNS is a tree. When you register example.com, only the parent (.com) needs to be updated. Each TLD is run by a different registry (to summarize) and registrars connect to it. Registrars do not update anything directly, this is a job for the registry

How does myemail@example.com actually work?

Anyone wanting to send an email to that address will at some point do a MX query in the DNS to find out which servers are Mail eXchangers for this domain, that is host configured to accept emails. When found, using SMTP, the emails are sent to one of those hosts.

Who's in charge of managing that email

The owner of the domain and then transitively the DNS provider used to be authoritative for the domain and the email hoster that will get incoming emails, and probably provide mailboxes and access to them through a protocol like IMAP

and what if someone else buys example.com 5 years from now?

If a domain changes hand, be it after expiration and deletion or just a change of owners (domains are a liquidity, there is a second market), the new owner of the name has full authority to configure it in any way it wishes.

Could I host my own email address at home if I own a domain name

Yes, but that means you need to have a server always on, to be able to receive emails. Of course you need to configure it properly, secure it, make backups, have a static IP address (not 100% necessary but certainly far simpler) and make sure it is not listed as residential or blacklisted if you want to send emails from there, etc. etc.

and would I want to do that?

Probably not, until you understand fully how the DNS, SMTP and IMAP works for example. Otherwise it is nice to learn but certainly not for production. It is not cost effective either if you factor in the electricity, Internet bill, time you put into managing it, etc.

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    Very precise answer, but one remark. There is a facility in SMTP, called ETRN (see postfix.org/ETRN_README.html ), intended for mail servers which don't have permanent Internet connection. It requires a "transient hoster" who'll receive (for this they will be specified in the MX record of your domain) and temporary store all your mail . When you connect to Internet, your mail server connects to this hoster and requests a delivery of all buffered mail. The rest mail processing is as usual, on your side. Hoster may optionally provide anti-spam and anti-virus protection. Nov 1, 2019 at 6:02
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    @NikitaKipriyanov Thanks, but yes there are A LOT of finer points not discussed there as it is just impossible for such broad questions.I know ETRN but I am not aware of any big email hosters giving that option,and I certainly wouldn't recommend it to anyone not already understanding SMTP and DNS well. You could as well point out about UUCP here that solves this need and is still used,and things like fetchmail that allows to grab messages over IMAP but reinject them locally as if they were coming from SMTP. In short, yes, many options exist. That may not mean home hosting is a good solution. Nov 1, 2019 at 6:11
  • The only thing triggered me is requirement of persistent connected and running server. Of course, there are countless caveats in the scope of the question. Nov 1, 2019 at 6:14
  • So you're saying it's something like this (in a tree): .com -> example.com -> my name server? What and where is the .com part of the tree, or the very topmost root? How come that doesn't e.g. get DDoS'd just because? I would think the internet would be very fragile. I'm guessing the ISP's play a major role in all of this, e.g. knowing how to convert .com into whatever the server IP is. How do ISP's keep track of these things?
    – Andrew
    Nov 4, 2019 at 15:43
  • One of my concerns with all of this is what if e.g. GMail, Live, etc. go down or get hacked or otherwise prove unreliable etc.? I don't like the dependency we have on large tech corporations to manage, secure, and provide our emails for eternity. One could create a new email address, but it seems that hosting it oneself, whether that be via. regular SMTP, ETRN, or UUCP, would be impractical and/or insecure. Theoretically one could hold onto their domain name for life.
    – Andrew
    Nov 4, 2019 at 15:55

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