Outlook 2010 cant send bulk/mass message

Hi

We have a Exchange 2010 Hosted server with SP1 Rollup 7-v2.
One of the tenant organization want`s to send out bulk/mass mail to his customers, about 1300 emails.

Have changed all the values in this article to 5000.
http://technet.microsoft.com/en-us/library/bb310760.aspx

The strange thing is that when the user add the emails in the bcc field, Outlook 2010 shows a message that the message only will be sent to 250 users. If we only add 250 users, the message show that the message will only be sent to 97 users.

Does anyone experienced this problem before? Or has a solution for this?

Thanks in advance