[PLUG] Question about header on sent e-mail message

[Rich Shepard]

   When I receive a response to an e-mail message I sent (top-posted,
naturally), and the sender includes the header of my message, it often
includes this line:

From: rshepard at localhost [mailto:rshepard at localhost] On Behalf Of Rich
Shepard

   My outbound mail is relayed through SpiritOne (nee Aracnet).

   I would like to understand why the domain is 'localhost' rather than the
actual domain, and how to fix it so outgoing messages have the correct
domain name.

   All thoughts welcome.

Rich