Нужна консультация, как справиться с подобной вещью


<***>:
xxx.xxx.xx.xx does not like recipient.
Remote host said: 550 5.7.1 <***>... Connect denied. IP name lookup failed for yyy.yyy.y.yyy
Giving up on xxx.xx.xx.xx.

<***>:
vvv.vv.vvv.vvv does not like recipient.
Remote host said: 450 4.7.1 Client host rejected: cannot find your hostname, [yyy.yy.y.yyy]
Giving up on vvv.vv.vvv.vvv.
I'm not going to try again; this message has been in the queue too long.