Hello,

This is most likely due to your hosting plan.

Make sure you do not have "Consumer organization" checked unless you want each email address under one hosted organization to be 100% isolated (this option is if you want to sell off single accounts similar to@outlook .com , where none of the accounts can see eachother).

Once unchecked on the hosting plan the only other option is the Mailbox plan, that also has an option to check the Hide from address book by default.

Regards,

Marco

Thanks again !!!

Yes that was the problem
Consumer Organization Support:
Enabled