I was studying the characters that can be allowed to be a part of an email address. Generally, we know that the email address is of the format localpart@domain, where localpart contains all alpha-numeric characters with special characters (special characters have some restrictions though) as per this wiki link.
My question is, apart from the alpha-numeric and specific special characters [, ], :, - and . are any other special characters allowed in the domain part of the email address? (this question is w.r.t US keyboard)
A domain name consists of one or more parts, technically called labels, that are delimited by dots .. Labels must follow the LDH (letter, digit, hyphen) Rule in RFC 1035: The characters allowed in a label are a subset of the ASCII character set, and includes the characters a-z, A-Z, 0-9, and the hyphen -. Labels may not start or end with a hyphen.
The "special" characters [, ], :, mentioned in your question are not allowed in a domain name. They could conceivably be part of an email address to a user's mailbox at a machine with an IPv6 address (user@[::1]) but email addresses tend to include fully qualified domain names rather than IP addresses.