on my edge server under the path(C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue) i can see a file mail.que which is 50GB. can this file size be reduced or deleted as i am running out of diskspace
The mail.que is not supposed to be reduced in size. It does contain the regular message queues, shadow queues and stores messages using the safety net functionality. This file is provide message transport high availability within a DAG. Depending on the Exchange org's transport settings (max size, safety net time, etc.) the file keeps (large) messages for the configured time. You can either move the transport database to a dedicated disk volume or (if you are sure that you won't loss any messages) you can stop the MSExchangeTransport service on that server, delete/move the file. As you are referring to the queue database on an edge server, I would stop MSExchangeTransport and delete the file. But I assume that the file will start growing again. That's what it does. And that's what it's supposed to do, especially when your users are allowed to send large messages.