Removing duplicate on priority criteria

Hello all site members ,
I am a newbie in MS Excel.
I have a excel sheet with 50K + records and consisting of 4 columns.website_name,email,fname,lname

The website name field consist of 1 among these 5 websites ebay,amazon,bestbuy,wallmart,target

I need to remove duplicate email id,such that email is which correspond to 'ebay' should not be present for amazon,bestbuy,wallmart,target..then in next iteration the email ids correspond to 'amazon' should not be there for bestbuy,wallmart,target...in 3rd iteration email ids correspond to 'bestbuy' should not be there for wallmart,target ..in 4th email id corresponding to 'wallmart' should not be there for target.
Priority order to keep the email id is ebay>amazon>bestbuy>wallmart>target.
I am wondering how can I do this.This is going to be a regular activity so I cant rely on manual cleansing.Can someone help me with the script/vba/macro to do this.or the logic to write program.

Thanks for your response.
The attached excel file has 2 sample work sheet one is the original list and second is the result sample.I have highlighted few records to explain the scenario.
Duplicate Email id which correspond to ebay(yellow) is removed for other websites(amazon,bestbuy,wallmart,target)...similarly duplicate email id which correspond to amazon removed for bestbuy,wallmart and target and so on.
The priority to keep email id in list is ebay>amazon>bestbuy>wallmart>target.
There are more duplicates in this sheet but I have not highlighted all of them to keep it simple.
Final goal is to keep all email ids for ebay...removing all duplicate email ids from other...then for amazon..then for bestbuy ..and so on ...However retaining corresponding row fields (website,fname,lastname)

Thanks JB for your response

I tried the code but it removed all rows rather than retaining the number of rows,Only cell value of 'email' column should go blank where the duplicate occurred keeping only one email id as per priority.
For ex in the attached file if you see the sheet 2, email id(yellow highlight) which is already present in 'Ebay' is left blank for 'amazon','bestbuy','walmart' and 'target' .
The row arrangement should not change in the result set.