This is normal. This is a unix program called "sendmail". It's what notifies you that you have a new PM. If it doesn't work (IE -- you get the error) the only problem is that the notification mail isn't sent. When the user logs in, they'll see the new messages.
Thanks for bringing this up... I should've posted it ages ago.
Rade wrote:Finally received a reply by posting in a thread at that Gaijin forum: