I opted-out project's alerts but I still receive them

I still receive notifications from projects I have unsubscribed using Settings > Account > Notifications > Fine Tune Alerts.

off option seems not to take any effect.

Any suggestions are welcome.

EDIT: Interestingly, I receive regression alerts from projects that have no alert rules configured.

Regressions and several other styles of emails come from workflow notifications which are a separate system from alerts. You can unsubscribe via the link in the footer but the subscription is per issue (outside of you default settings).