Errors because of Deffered emails

[mansuper]

Hi

Does anyone know how to handle the deffered emails?

When I check the daily report as an admin, I can see everyday some Errors like this

Errors
2006-11-20 13:13:31 deferred (xxx.xxx.xxx.com: Name or service not known)
2006-11-20 12:37:45 deferred (Authentication failed: cannot SASL authenticate to server xxx.xxx.xxx.com[xxx.xxx.xxx.xxx]: generic failure)
2006-11-20 15:48:35 deferred (xxx.xxx.xxx.com: Name or service not known)
2006-11-20 14:30:15 deferred (xxx.xxx.xxx.com: Name or service not known)
2006-11-20 12:27:08 deferred (xxx.xxx.xxx.com: Name or service not known)


I guess these emails are lost as many of my zimbra users say that their recepient didn't get the email.

So, how to handle these emails? I mean how can I send these emails without being deffered? Where does these deferred emails get stored?

Thanks in advance.