sending to bulk mail addresses crashes outlook

[RabbieBurns]

I'm not sure if this is an exchange issue or an outlook issue, but I have one shared mailbox, that whenever either of the users with the mailbox mounted tries to send to multiple (10 or more) mailboxes, outlook will lock up and become non responsive.

 

Could it be something as simple as just a too low spec machine? Or is there something inherantly wrong with either Outlook or Exchange 2010 causing this to happen?