Does the part to the right of at sign have to be valid website address?

Solution 1:

No it does not have to be the same. Email uses a different protocol than websites, and there's always the option to have non-existing domains for internal emails (inside companies).

For example, if I have a domain controller which hosts MyDomain.local, and I have an exchange server inside this domain, I can have [email protected]

If I do not host a webserver and disable everything else that makes websites, http://MyDomain.local will not work.

On top of that, given that this is an internal address only, it will not work from the outside either.

If we talk about external email addresses, then the following matters:

The email address has 2 parts: the user and the domain + optionally subdomains.

If we take for example: [email protected], then LPChip is the user, email is the subdomain and example.com is the domain.

The domain has MX records that tell where email is located. It is this route that is used to deliver email by the SMTP protocol.

Now its also possible to have an @ in a website url which usually means username@website but can also be used as @ char in the website's uri.

For example, the following website address is valid: https://example.net/owa/[email protected]

The uri here is /owa/[email protected] and does contain a @.

Another example is this:

ftp://[email protected]

Solution 2:

No, website and email address have basically nothing in common.

The right part of [email protected] means that you send email to a domain called microsoft.com. The protocol used to send email is SMTP.

But the url http://www.microsoft.com/ means you want information that are hosted on a server called www. The protocol used is HTTP.

It is not required that these two parts exists for both protocols. And the contrary is also valid. For example, you may have a support website like http://support.dell.com/ and have no email address whatsoever @support.dell.com.

Solution 3:

[email protected] is a working email address if the MX record for example.org points to a working mail server that accepts mail for that email address (i.e. listening on port 25 and handling SMTP requests).

http://example.org/ is a working URL if the A record for example.org points to a host running a web server (i.e. listening on port 80 and handling HTTP requests). If there is no web server at example.org, most browsers follow the standard recommendation to also try http://www.example.org/.

Look up the relevant Internet RFCs, e.g. for TCP where it explains ports, if you want more details.

These are two different services that are completely separate. A server might be running one or both.

As Tersosauros points out, "valid" has a technical meaning of not-a-syntax-error, not necessarily "working". See that answer for more.

Email is special in terms of DNS. MX records can list any mail server as the Mail-Exchange for a domain name. All other services (ssh, ftp, http, https, etc. etc.) use the A (IP Address) record directly, rather than first checking a "what's the FTP server for example.org" record for an extra layer of indirection. This is irrelevant for this question, though. All Internet services are orthogonal, and might or might not be present for any given domain name.

(port-based routing by a router/firewall can split up the http and the ftp traffic (for example) to different servers for a single IP if needed for large sites, so other services aren't missing out from not having their own indirection records like email does.)