How many @ symbol can be in an email address?

Question

Is there any rule for having a specified amount of @ symbol in any email id. Just come to my mind if we\'re to check if an email id is valid or not using PHP.

Answer 1

There can be any number (within the size limits of an email address) except that the last one must be the separator between the domain name and the "local part".

If an @ or any other "unusual" characters (as defined by RFC 5322) exist in the local part it MUST appear in quotes, e.g: "user@something"@example.com