This happens on a range of machines. I've just repeated the phenomenon on a PB 5300c, Performa 5300 and a LC 630. All were running client 5.0b8.
It doesn't happen when you resave a message but if you create a new message with the same title. The PPCs gave error message type 11 and the 68k type 1.
(NB Any chance can we have an outgoing mail folder in the user's mailbox and an indication of the message title too in the next release?)
Regards,
Chris
********** Chris Unsworth School of Art & Design, University of Derby, Britannia Mill, Mackworth Road, Derby DE22 3BL