问题
How many subdomains are possible for an Email address?
For Example: something@something.co.uk.uk
like that....
回答1:
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).
来源：https://stackoverflow.com/questions/5087426/how-many-sub-domain-are-allowed-for-an-email-id