Triggers do not allow usage of regular expressions.
I’m sure you want to ensure that specific users (maybe because they requested) do not receive trigger based mails.
The best way to achieve that would be a custom object for user accounts that you can check on.
If we’re talking about specific aliases from systems like noreply Zammad does have a function for that. If last option is relevant to you, you may want to check Block Notifications settings within one of the email channels. ( Settings — Zammad documentation )