Is there a way for a customer to notify another customer of a created ticket, similar to CC: in an email?

[Steven Garbarino]

Often a customer will want to notify a coworker or supervisor that they have created a ticket - is there a field I can create where they can input their username or email to send them a copy of the ticket as well?

Thanks for the help!  

[Fabrizio Galletti]

Is that enduser a JIRA or SD user? 

If "no" then you can use a different plugin like: 

JIRA enterprise mail handler or Script runner with a post function

If Yes: you have to try to put him as "collaborator"