There are many ways to learn to code these days. From coding bootcamps like Flatiron School to online courses to totally free beginner resources. The best way to learn to code depends on many factors, but the most important one is you. See what course is best for you.
Any one of these can trigger and email to you if you are on one of their DGs. Hence you receiving an OOO for a recipient you never sent to. OOO responds to current sender - it doesn't matter who the email originated from.
Make sense?