Smiley faces are just grouped keystrokes, and depending on the program you are using, depends on how they are programmed to interpret the group. If the program is not programmed to know what certain keystrokes together mean it will not present the face but just leave it as a mix of letters/symbols ( lol ) and (

) are the same but this board is programmed to expect a : before and after the text to know it represents a smiley or its just text, another example is ( confused ) or (

) these are both the same other than the : before and after. When the :xxx: appears the program looks for the pic asociated with it in a database and presents it in the place of the text/symbols writen on the keyboard
Some email programs have a limited amount of smileys and others can be installed, but personally i almost always use plain text in emails as to see them you must read/see them in HTML code. HTML code is used to describe the different aspects of an email, letter size/colour, background, etc. and is invisible to you and can be dangerous to the pc/mac security as hidden malicious code can be inserted and activated without your knowledge.
hackers, spammers and hijackers use this to the full to hack or propagate virus/Trojans or even overtake your pc
Sorry if that was a bit long winded, as also posted you can save them to your pc as images and insert the image into your email, although they could appear small without the attached html to describe size