An 'EDM' normally refers to an eMail database that the brand, site or business owns that can be used to send eMail updates to. Generally a media publisher will try and build their eMail database as one of their most cost efficient ways of reaching an existing audience. The overall number might look impressive but without any context to the 'Open % Rates' or 'Click % Rates' having a huge database has little meaning. For a website audit I completed in 2020 a site owner had over 10,000 people on their eMail list, but less than 10% open rate so really only 1,000 people were generally opening the eMail which isn't very useful to a brand owner investing money to advertise.