The arroba has long been sometimes written as @, which is a kind of stylizeda. So when AT e-mail developed, it became a natural step to simply use the termarroba when the symbol was used in addresses as well.
DASH Is a punctuation mark that is similar to a hyphen or
minus sign, but differs from both of these symbols
primarily in length and function.
UNDERSCORE Alternatively referred to as a low line, low dash, and understrike, the underscore ( _ )
FORWARD SLASH The forward slash or slash as it is known is a widely used punctuation mark, denoted by the symbol - '/'.
BACKSLASH A short oblique stroke (\): used in some computer operating systems to mark the division between a directory and a subdirectory,
links:
http://www.estacioninglesa.es/blog/guias-ingles/como-se-dice-arroba-en-ingles/
http://www.computerhope.com/jargon/f/forwards.htm
http://en.wikipedia.org/wiki/Dash
http://www.buzzle.com/articles/forward-slash-vs-backslash.html
http://en.wikipedia.org/wiki/Backslash
http://spanish.about.com/od/spanishvocabulary/qt/at_symbol.htm