We use 'Direct'. The problem I saw in the message header source was that Adagio uses +0000 for the time zone designation when it creates the message and The Lightinng plug-in in Thunderbird (the only place in TB where I was able to find a time zone selection menu) is set to 'America/Los Angeles' - which seems to cause Thunderbird to subtract 8 hours from the incoming message.
Well, it's not that big a deal. It just would be nice if it matched.;-)