qmail mails not sent correctly

[K3yMaster]

Hi,

I've installed qmail using the guide http://www.gentoo.org/doc/en/qmail-howto.xml , but I'm having problems with some domains not accepting my mails for some unknown reason.
I send a regular mail and check the logs where I can see that the mail is accepted by the remote server, but the mail is not received by the user
At the moment I have this problem with 2 domains, but only I have a problem with sending the mails. If I use a hotmail account there is no problems.
I can without a problem send mails to hotmail.com, yahoo.com etc.

Below is some info on my installation:
Kernel : 2.6.5
qmail : 1.03-r13 (with ssl)
qmail-scanner : 1.16-r2

I hope someone can give me some hints on how to fix this issue..

[K3yMaster]

Hmm..

So I guess no one has an idea of what might be wrong.. I know its a strange thing that some domains dont accept my mails.. Its just that I've sent mails to these domains prior to installing gentoo and the latest qmail.. My old installation with redhat 9 didn't have problem sending mails to these domains.

Could the problems be linked to my certificate ?