Returned mail: see transcript for details

[Post Office]

This message was undeliverable due to the following reason:

Your message was not delivered because the destination computer was
unreachable 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.

Your message could not be delivered within 4 days:
Host 90.88.12.249 is not responding.

The following recipients did not receive this message:
<sendmail na linux.cz>

Please reply to postmaster na linux.cz
if you feel this message to be in error.