Temporarily blacklisted IP Address

I cannot access my email via Outlook.  When trying to receive my email I get the following error:

Receiving' reported error (0x800CCC92) : 'Your email server rejected your login. Verify your user name and password for this account in Account Settings.  The server responded: -ERR [AUTH] Temporarily blacklisted IP Address - try again later'

This happened a while ago and did clear up after a few days.  But here it is again.  After a week of "trying again" I am still getting the same error.  I've been a customer for 10 years, why would my IP address get blacklisted?  And how do I prevent it from happening again, as it has happened twice in the last month or so.

Thanks in advance.