The Exchange Server is affected when I assign the email account to the user

I Install Joget and after I configured the email accounts, the exchange queue incresed and to send one email took more than 7 minutes.

I disconnet the laptop from the network and the service return to the normally. I changed the email accounts to gmail accounts and the service was normal. The I change again to the corporative accounts and the server had problems again.

Do you know why and how can I solve the problem?