lead's duplicate through email "Domain"?

lead's duplicate through email "Domain"?

Hi,
is it possible to check for email "domain" duplication while creating the lead?
Scenario example:
Sales 1: add's a lead from company XXX and used email : john@xxx.com

two days later:
sales 2: adds another lead from the same company but used a different email with the same email malcom@xxx.com

this is considered to us as duplicate lead (since they're both the same account)...

how can we overcome this challenge? or at least notfiy the sales 2 guy that there is an existing domain same as you're adding..