1. Create a Scenario for matching by Email only

1. Go to tab DC Setup.
2. At left, open the Object you want to find duplicates for. 
3. Open the object's Scenarios tab (the object probably opened on that tab).
4. Click Add New Scenario .
5. Enter a name for the new Scenario, e.g. "Email Only", and click Add .
6. Set the Threshold number at 100%, because we are looking for exact matches on Email Addresses. Only records that will match 100%, based on email address, will be shown in the duplicate results list. 
7. Leave the Empty Fields value at "Disregard". Since we're using a scenario with only one field, this setting is irrelevant. Learn more about empty fields.
8. At Apply To, select "DC Job". This makes the scenario available to be used in a Duplicate Check Job. You can add more options here to use the scenario in other places as well.
9. Click Add New Field .
10. As Field, select the "Email" field. 
11. Leave Synonym Matching and Frequent Words at "None", since we are looking for exact matches on Email Address.
12. At Matching Method, select "Exact".
    
    Delete

    If you want to find duplicate records with almost identical email addresses, you can also decide to use "Fuzzy" matching here. This way you can find duplicates with minor spelling mistakes in the email address.

    Matching method "Email Address" is another option. It compares email addresses based on similarity rather than on exact match, matching the addressee part differently than the domain name part. 

    However, in both cases the Threshold should be set to a bit under 100%, e.g. 95% or 98%, since these matching methods will also find email addresses that are almost but not exactly the same.

    Read more about Matching Methods.

This is what your scenario should look like:

2. Start a DC Job using the scenario

1. Go to tab DC Job.
2. At top right, click + New Job .
3. Enter a job name, and select the Object you just created the "Email Only" scenario for. 
4. At Scenario, pick the "Email Only" scenario you just created. Make sure no other scenarios are selected.
5. Add a filter to narrow down the search (optional).
6. Click Next.
   
7.  Add a Schedule or Auto Merge if desired. Click Next.
   Select where to process the DC Job and click Start.
   Read more about these steps in DC Job - Find Duplicates in Batch‍.

The job will now start and appear in the DC Job Overview. Its results, on the DC Job Results Overview,‍  will show only those records with identical email addresses.