Say I am running a website that publish news/blog/information about products X,Y,Z. Here X,Y and Z all three are different categories. If a person who is interested in news about X, he/she might like to know anything about Y or Z. (For example, If X relates to 'Technology' then Y relates to 'Restaurant' and Z something else)
So my question is, In case I am running an Email campaign, Should I send the Email with X related update to those subscribers who subscribed to get X related Information only Or it must be send to all the users?
If I want to send Email of X updates to subscribers who want to get X related information only, then what procedure/format can be opted? Is there any benefit of tracking each user according to their interest?