Click the File tab, and
select Account Settings...
On the E-mail tab,
select your POP account and click Change...
Change the following fields:
Incoming mail server: mail.your_domain.com
Outgoing mail server (SMTP): mail.your_domain.com
Require logon using
Secure Password Authentication (SPA): Leave this option unchecked.
Click the More Settings... button
Select the Outgoing Server tab.
Verify the box next to My outgoing server (SMTP) requires authentication is checked and select Use same settings as my incoming mail server.
Click the Advanced tab, and Click the Use Defaults button
Verify that the settings were reset to the following:
Incoming server (POP3): 110 (This server requires an encrypted
connection (SSL) should NOT be
Outgoing server (SMTP): 25 (Use the following type of
encrypted connection should be set to NONE)
Click Next, and then click Finish.