I have configured e-mail in stores and I have gone through several situations, (Clear cache, check default,) and never had problems, but there is a store that can not find the error.
Bavatos.com.br
When I'm at a local address, it works. When I'm at a production address, it does not work.
It works: http://localhost:15536/Admin/EmailAccount/Edit/1
Does not work: Http://bavatos.com.br/Admin/MotionThemeAdmin/Settings
Settings are the same in BD. (Its equals) The server is ok. I really do not know what it is, has anyone had it?
I am guessing that you have "force WWW. prefix" enabled in your general settings and that this: http://bavatos.com.br/ is not "found" because it includes no WWW.
The error you shared with us definitely means that nopCommerce cannot find the remote server at the address specified.