Exch Client not redirected to new server

Hi all,
After moving all mailboxes from SiteA (Server1) to SiteB (Server2), I remove all the Site Connectors to SiteB and deleted Server2 using SiteA Exchange Administrator. KCC successfully carried out but when the user log on to email, the exchange profile does not redirect the client to point to Server1 causing the user unable to open the mailbox.
Why the exchange profile isn’t updated automatically while Server2 still alive. What can I do to change all the users’ exchange profile to point to Server1 instead of the original Server2?
Thank you in advance.