Some of this depends on which POP3 account your working with, but one of these suggestions may, at least, point you in the right direction.
(Type the Q number in the search box at technet.microsoft.com)
1. Start Outlook.
2. On the Tools menu, click Services.
3. In the Services dialog box, click your Internet E-mail account.
4. Click the Servers tab, and then click "Log on using Secure Password Authentication" under Incoming Mail Server.
(Some services want this turned off, try both)
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