How to disable vbulletin sending e-mails to a certain user?

[postcd]

Do You mean that to prevent topic reply notification e-mail being sent, i have to remove user thread subscriptions? Because it is not good to do, since user may return, change e-mail, expecting notifications and not receiving these. I would have expected that Your suggestion "Edit user & delete the email in the account." would be enough.

i put them in a secondary group & use the notice system to fix their email.

Thanks, I have put a new notice for "Users Awaiting e-mail confirmation" group. /admincp/notice.php that user may need to change their e-mail and if unable to login (placing user to awaiting email confirmation group- i asked them to contact me with old/new email, i do not know if good idea or if i will be able to verify user is really the account owner)