Best way to move an email sent directly to a user to a ticket

Best way to move an email sent directly to a user to a ticket

As we begin to migrate to Zoho Support, emails related to existing tickets are still going direct to a user.

What is the best method to transfer that to the existing ticket?  Add the email contents to a comment?  Or just forward the mail to the support email and then merge or transfer to the existing ticket?

If an email comes in related to a new ticket direct to a user, should he just forward that to the support email, or create a new ticket and list the sender as the ticket contact and reply from there?

Thanks - just looking for some best practices.