Returned mail: Data format error

[Post Office]

This message was undeliverable due to the following reason:

Your message was not delivered because the destination server 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.

Your message could not be delivered within 6 days:
Mail server 129.83.51.78 is not responding.

The following recipients could not receive this message:
<elektro at tesla.hu>

Please reply to postmaster at tesla.hu
if you feel this message to be in error.