The reply should be sent as a response to one of the emails previously generated by the support case, above the line starting with three octothorpe (#) symbols
See below for an example email response to a support case:
If the reply follows this pattern, then it will be readily visible to the support engineer in their case view:
If the above steps are not followed then any emails to firstname.lastname@example.org will create a new case, using the subject line of the email as the subject of the new case.
This creation of new duplicate cases can cause confusion and delays in our responses to the original case. Keeping everything contained within a single case allows us to avoid this problem and focus entirely on the issue at hand.
Note: try to avoid CC-ing in email@example.com, as this will create a support case as a result (unless this is intentional!)