How can I see which user created a campaign in Sitecore EXM, and which user scheduled or sent the campaign?
Assuming you're using Sitecore 9 with ExM built in, all of the ExM emails are stored in the following location:
If you look inside the date named folders you will find the email campaigns you created in there. Each of these has the standard Sitecore fields for Created By & Updated by, in the Statistics section. This will give you the name of the user who created the campaign.