When i create user it takes long time to send email from 15 minutes up to hours.
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From the Admin console I've been able to create new users, intentionally giving them a very simple default password, and been able to log in and change that password as that user within seconds.
If you're trying to create user through smart service, I highly doubt that the smart service is the problem. If you're talking about the length of time before the email arrives, I would look at your mail server, and then your mail client, and see if you can find how far downstream or how far upstream the problem lives.