This Message was undeliverable due to the following reason:
Your message was not delivered because the destination computer was
not reachable within the allowed queue period. The amount of time
a message is queued before it is returned depends on local configura-
tion parameters.
Most likely there is a network problem that prevented delivery, but
it is also possible that the computer is turned off, or does not
have a mail system running right now.
The queue containing messages destined for yahoo.com was expired by the postmaster of imsa4003.i.softbank.jp.