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How many subdomains are possible for an Email address? For Example: something@something.co.uk.uk like that....

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Yoko Zunna
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1 Answers1

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There isn't any constraints based on subdomain count.

There is limitation of lengths parts of e-mail address in RFC821

user

The maximum total length of a user name is 64 characters.

domain

The maximum total length of a domain name or number is 64 characters.

path

The maximum total length of a reverse-path or forward-path is 256 characters (including the punctuation and element separators).

limitations in RFC2821

local-part The maximum total length of a user name or other local-part is 64 characters.

domain The maximum total length of a domain name or number is 255 characters.

and newest in RFC5321

4.5.3.1.1. Local-part

The maximum total length of a user name or other local-part is 64
octets.

4.5.3.1.2. Domain

The maximum total length of a domain name or number is 255 octets.

4.5.3.1.3. Path

The maximum total length of a reverse-path or forward-path is 256
octets (including the punctuation and element separators).

Community
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acoolaum
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    +1, but note that this RFC was superseded by [RFC 5321](http://tools.ietf.org/html/rfc5321#section-4.5.3.1) and the limits are now much larger. – mpontillo Feb 23 '11 at 06:08
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    @Mike, thank you. I've added information from RFC5321 in my answer. – acoolaum Feb 23 '11 at 06:17