Weird problem happening with CC Fields

[Un Area]

We are experimenting this weird issue.

1. We have a domain that has email forwarders to other hotmail addresses.
Ex: john@domain.com -> john@hotmail.com
Ex: mary@domain.com -> mary@yahoo.com
etc

Ok, when John enters to his hotmail account and write a mail to his "forwarder address" john@domain.com, he receives the email in his hotmail account john@hotmail.com.

When he writes a message and in the To: field adds john@domain.com, jeff@domain.com, mary@domain.com, the messages are received fine by each one of them.

Now when he enters in the To: field john@domain.com and in the CC: field jeff@domain.com, mary@domain.com messages doesnt arrives.

What is going on? Its only affected when the forwarders are inserted in CC: field. If they are inserted in the To: field separated by commas, the mails arrives fine.
Cause the logs tells me that the message was delivered. I dont know if it has to do with SPF records that uses hotmail, maybe that is deleting the email.
The weirdest thing is why is getting through the emails inserted in To: field and no the ones at CC: fields.


Thanks