IDs in MySQL, standard IDs or alphanumerics?

[Tikindros]

I'm thinking of this, if I make a web site for a specific university's students should I make the ID as standard IDs on MySQL (integer, auto increment) or should I give the IDs as how is their email address is, like if the student's email address is [email protected] then his/her id is e12234 (on my web site). Is it ok, what about performance?Edit: Also, there are such email addresses:[email protected] (exchange student)[email protected] (this is a professor)