"Email Account -> send copy to" issue
The bug is happened when you create email domain and email account with some "send copy to" value and you delete domain. After it, when you create same domain with same email account, "send copy to" value seems to be clean, but server is still trying to delivery copy of email to account which you've previously declared. To fix it, need to add to empty "send copy to" field any email, and afer update, you need to clean field and again save changes. I've lost about 40minutes to track it :D
Cheers, bitebyte