Outlook Freezes When Composing a New Email or Replying

Configure Outlook in Cached Mode

In Outlook, on the File menu, click Account Settings, and then click Account Settings.
Select your Exchange account, and then click Change.
Click to enable the Use Cached Exchange Mode option.
Slide the Mail to keep offline setting to the setting that you prefer.
Click Next.
On the prompt that the operation you selected will not complete until you quit and restart Microsoft Outlook, click OK.
Click Finish, and then click Close.
Exit and then restart Outlook.