qmail-smtp slow!

[Gan]

Hello, I'm using qmail for several domains for relaying , i went into trouble since few days ago when i moved my server to another network , the thing is when i'm telneting to smtp port of my server there is a latency (more than 30 sec) before qmail answers me 220 xyz.xom ESMTP the only thing changed ( that i know) is that full C class network changed to sub 128 network . Help me ! and thank you in advance!