Ozarkopa,

Most E-mail may look like it is received by the same person but in fact could be sent from a different IP address that is phishing the real E-mail address.

Since you stated that the blocked sender address wont retain in the block senders list, this is a sign that your outlook client could be corrupt.

I recommend running the below command line switch:

1. Click Start.
2. Click All Programs.
3. Click Accessories.
4. Click Run.
5. Enter the following in the Run dialog box (with quotations):
   "c:\program files\microsoft office\office14\Outlook.exe" /cleanprofile

This will fix any registry errors found in the client.

Hope this helps