Thanks
2 answers
Refer Salesforce Object to query the same from Apex
https://developer.salesforce.com/docs/atlas.en-us.sfFieldRef.meta/sfFieldRef/salesforce_field_reference_EmailMessage.htm
https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_objects_emailservicesaddress.htm
Refer LocalPart field for the address from EmaildomainName
Hope that helps!!