Mail System Error - Returned Mail

[MAILER-DAEMON]

The message was undeliverable due to the following reason(s):

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 2 days:
Mail server 106.109.138.65 is not responding.

The following recipients could not receive this message:
<editors na linux.cz>

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