Hi, Some of my customers are sending me their return email errors so I can see whats the problem, now some of the mailer daemon says> <firstname.lastname@example.org>: Sorry, I couldn't find any host named tnc.org.gt. (#5.1.2) <email@example.com>: Sorry, I couldn't find any host named fcg.org.gt. (#5.1.2) <firstname.lastname@example.org)>: Sorry, I couldn't find any host named defensores.org.gt). (#5.1.2) <email@example.com>: 126.96.36.199 failed after I sent the message. Remote host said: 552 5.6.0 Headers too large (5128 max The domain name is not pingable, it does not respond BUT the domain name is registered and exists, they must have some kind of firewall. My question is> the qmail can send email to a non pingable domains????? because I have get to many errors, to many of this mailer daemons telling me that the domain name couldn't be found when the domain exists and is running. Any ideas????