Mail app only shows reply in inbox

[CTHarrryH]

I see inbox normally but when I reply to an email - the reply shows up in inbox and I can't find the original email anywhere.
My iPhone shows fine - just the mail app on my El Capitan MBP. This just started recently. I can't find setting or ?? that would cause this. Grouping by conversation is off.

Thanks

 

[ToomeyND]

My wife just had this happen yesterday on her brand new (2 weeks old) rMBP synced with her gmail account. On the sidebar, instead of showing the original sender of the email, it showed my wife's email address, less than helpful...

After a few attempts to change settings, I deleted the account, deleted the contents of the ~/Library/Mail folder, restarted the computer, and added the gmail account back to mail.

I haven't checked in with her today, but I believe that fixed the issue. I suppose I am not "solving" the problem here, but hopefully it helps you get back up and running.