Disable ANY type of mail notification on USER BASIS

[fman]

Hi:

I'm using Mantis:1.0.1 on linux
I need to configure several users (specially REPORTERS) in order to suppress ANY KIND of e-mail notification
no matter type of activity done on ISSUE.
I've tried unchecking all config on the USER ACCOUNT, but (may be I've done something in the wrong way) mails
continue to arrive when a developer updates the issue.

Any hint ?
Any reference to documentation?

Thanks a lot