o Is there a way for the customer to keep track of a ticket through email?
Agent may select methods to have customers emailed their responses/updates. Of course the customers email must work.
o Does otrs have to be on the same machine as the mail server that handles its messages or, say, it can check and download them like a normal user would?
No it doesn't have to be on the same server.
If so, what would happen if the link is severed?
The server will generate 'error' tickets stating that it's unable to send/retrieve messages.
o If a help desk person wants to reply to customer, must she use the web interface to send a reply or can she user her normal mail client and her reply will (through cc: or whatever) be added to the ticket?
Out of the box... agents have to use the web interface. A list member posted a workaround which added agent functions via email (not sure of the specifics). gl...