Reasons that will lead to an unread email to be down-thumbed based on Subject alone:

1. I don’t believe that your Subject truthfully captures what would be in email body
   
2. You’re blatant clickbait – I can sense it immediately
   
3. You might be too long an article for my schedule, so I rather not postpone or keep procrastinating, but delete the mail
   
4. Great! Nice to know. The subject already tells everything. Don’t need body. Deleted.
   
5. Sounds like random noise incoming, I’ll muffle it. Deleted
   
6. Yesterday’s weather notification from a system – deleted. Future-referencing weather notifications are much more useful.
   
7. Your content seems to be bit too much of a mixed plate, a “smörgåsbord” – I don’t want confusion. I’m a flow-baby, or at least right now in flow mode (TM)
   
8. You are most likely a robot posting the email, without any viable payload to be expected..
   
9. Some random notification coming out of a list I once subscribed – I’ll unsub, this was my bad! Note to self: don’t subscribe on remotely interesting project’s bug tracking lists.
   
10. The content might be relevant job post, but in a format (from HR system) that reflects the organization is outdated – I want modern and fresh organization. Everybody wants that.
    
11. SORRY I DON’T DO CAPS
    
12. Subject says: ‘Please don’t reply to this mail’. No worries. Click.

Cheers!