cannot delete specific email / tabs are useless
I found that I cannot delete specific emails when they become part of a "conversation." This was especially annoying when I received a mailer daemon error from a reply that I sent and I wanted to delete only the reply so I could start over. Also, I received a mailer daemon error because I was flagged for suspicious activity even though I was the one to sent the reply.
When I deleted the email from my sent folder, hoping it would only delete my reply, it deleted my entire conversation. When I restored the conversation from the trash box the emails were all sent to my inbox rather than being sorted back to their original folders. As far as I can tell, there's no way to sort out the emails in a conversation just as there is no way to specifically delete an email from a conversation.
During this process I noticed that by the end several tabs in my email had been created, none of which had been used or were even relevant. They were just an eye sore.
