What to Do When You Receive Duplicate Messages in Outlook Express

If your default email account is either an IMAP account or a Hotmail account accessed directly, you may see two copies of every message in your Inbox.
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How to prevent seeing duplicate names when viewing the Select Names window in Outlook after clicking To:

How to prevent sending duplicate email messages in Outlook

How to prevent duplicate appointments in Outlook

How to remove Outlook duplicates, including email, contacts, appointments, and tasks