some customers don't wanna get notification mails
it would be great to have an option at cusomer data not to send such mails

it would much better, to have that option an the ticket too and its set to the value of the customer on ticket creation.
so we could see if the customer usually gets mails but decide for an other option at creation of a ticket

alternatively a condition "contains not" at ticket automation rules could be a workaround
send mail if customer name contains not "(no mail)"