Mail question

[Alexander Bogdanov]

Hello.
I'm student from Latvia. I'd like to ask you a question about Postfix
mail system under FreeBSD.
I have such problem: target is to allow user to change his mail
account's password by himself. For example, I set password for his
account, and maybe, user doesn't want me to know this password, so
he'd like to change it!
The question is: HOW? 

I'm looking forward to hearing from you.

-- 
Best regards,
Alexander Bogdanov (GSM: +3716100890).