JETI: comments are send to customers when internal comment added

Hello,

I have a problem.

When an internal comment is added to an issue, the customer (with customer-account) who is set in watcher-field gets a notification. That is bad!
An external user (no account) whose mail-address is stored in custom field dont get a notification at an internal comment. That is ok.

Can you please help me so that the customer (with account) doesnt get anymore notification for internal comments?

Best Regards
THorsten