help in email developing

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hi
i just started with developing email code
but iam still not sure about message body
i've been thinked about how to sign up a new user and how to validate member access , when the user enter his nickname and password it will be stored in a hashtable
and when he want to login the prog will compare the enterd values with stored ones. but what i am not sure about is the message body. because all parameters are just one line values and message body is different.
what i am thinking in to solve this problem is to call the message body and other parameters individually and put them on the gui but i am not sure if it is possible and how far it is effective
what do you think? any suggestions?