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I'm specifically looking for the minimum length of the prefix and domain.

I've seen conflicting information and nothing that looks authoritative.

For reference, I found this page which claims that a one character email address is functional:

http://www.cjvandyk.com/blog/Lists/Posts/Post.aspx?ID=176

I tried validating email addresses at Gmail and they expect prefix greater than or equal to 6.

These are obviously way off.

My web framework expects prefix greater than or equal to 2.

Jerry Chong
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David Watson
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4 Answers4

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The shortest valid email address may consist of only two parts: name and domain.

name@domain

Since both the name and domain may have the length of 1 character, the minimal total length resolves to 3 characters.

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    I know this post was a VERY long time ago, but most domains end with ".com" so we have 4 characters there. Just "@gmail.com" has 10 characters, so the min for Gmail could be 11 characters. – AlexFullinator Jun 09 '23 at 18:55
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    _Patrick Mevzak_ answers the domain part of the question at length [here](https://stackoverflow.com/a/49098802/12715438). Theoretically, a domain with only one character is possible in an Intranet environment. So, the accepted answer is accurate— the smallest possible email address is three characters—`a@b` However, the current IANA root starts with ccTLDs, which are two characters. So, the shortest valid email address on the web is six characters—`a@b.cd` – killshot13 Aug 25 '23 at 11:50
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well the problem is really the question.. email depends on if it is sent over the internet, or within a closed system (eg intranet). over the internet, I believe x@y.zz is the shortest email possible (e.g. google's G.CN for china would result in the shortest email adress possible, e.g. i@g.cn, which is 6 characters long). on the intranet however, it is an entirely different thing, and i@y would be possible, which is just 3 characters long.

Mark
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    You can set up an MX or A to answer for a top-level domain, so that you could have somealias@com. I believe that's been done. You can set up a new top-level domain on your own name server only visible to machines you control, and thus make a one-letter top-level domain, for a minimum of 3 letters including the '@'. – kaleissin Mar 21 '13 at 12:29
  • given this i think the proper answer for a valid "internet" email address will be a minimum length of 4 (including . and @), and for an intranet a minimum length of 3 including the point. – Pedro Emilio Borrego Rached Oct 19 '16 at 15:40
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I believe the standard you are looking for is RFC 2822 - Internet Message Format

More specific info on email address restrictions in RFC 3696 - Section 3

To quote the spec:

Contemporary email addresses consist of a "local part" separated from a "domain part" (a fully-qualified domain name) by an at-sign ("@").

So three characters is the shortest.

I originally got this info from Phil Haack's blog post.

Community
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Josh Stodola
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Many mail-servers will not accept the email-address if there aren't at least 2 characters before the @. That doesn't make it an invalid address, but if the servers don't know that, it sure can lead to a lot of problems.

Lars Munkholm
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  • Glad I found this. I'm testing out a new email regex to use in an open source validation library and our current test suite fails with the new regex with `n@p.fr` but passes with `nn@p.fr`, so it seems like this new Regex I obtained asserts that the local part must be two characters long. I can't seem to find out why, but it must be this. It's probably best to enforce this minimum length then. – Matt Welke Mar 13 '21 at 23:55