How email works: why a fake email from your boss can reach your inbox
MX records: how an email finds the mail server of a domain
An email address holds no place, only a name after the @. So how does an email find the one computer that takes the mail for that name?
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An email address has two halves. After the @ comes the domain: the name of the place that takes the email. Before it comes the mailbox at that place, yours.
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So Rono's server asks DNS, the system the internet uses to look up names. Your phone asks it too when you type a web address, but this question is a different one: who takes the mail for woodshop.example?
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The answer is an MX record, short for mail exchanger. The workshop published it in DNS, and it names the server that takes the workshop's mail. One more question gives that server's IP address, its number on the internet.
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Rono's server connects, and the workshop's server lets it in at once, with no password. It takes email from any server on the internet. It has to: anyone in the world may write to the workshop.
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It reads the From line, finds Miva's own address, and has no reason to doubt it. Into your mailbox the email goes, with the real emails of the day.
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The workshop's server knows one thing for sure: the IP address of the server that is talking to it. It does not know which servers really send the workshop's email, so a fake of your own boss walks straight in. Can anything stop it?
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Quick check
Quick check.
Show the answer
Who takes the mail for gardenclub.example: the MX record of the domain after the @. Sam's part is not in the question: the club's server finds Sam's mailbox itself.
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Go further
One more thing about MX records.