Look at these individually:
Send me the details
Send I the details
Clearly, me is the correct choice. (me is an object, whereas I is a subject)
As for whether it is direct or indirect:
First, find our verb. (send)
A direct object answers the questions "What?" or "Whom?"
An indirect object answers the questions "To/for what?" or "To/for whom?"
The direct object is the details.
Send what? Send the details in an e-mail.
Me is an indirect object.
Send the details to whom? Send them to me.
note While "me" can answer the first question (send me in an e-mail) it does not make sense.
b. me: indirect object
