When a support ticket's status changes to solved or closed, email the member who opened it.
Thank them, name the ticket, and ask two questions: how satisfied they are with how it was handled, from 1 to 5, and whether anything still needs to be done. Ask them to answer in this short form: [your survey form link].
If an administrator opened the ticket, or the member already got this email for the same ticket, do nothing. Write in the member's language.