As documented here:
There are 2 places where you need to enter the smtp settings, you only set one of them. You need to also make settigs in system.net mailsettings section of web.config
New user email confirmation, password recovery and a few other things (things built into ASP.NET) use the settings from system.net mailsettings section.
Hope it helps,
ps: please, do me a favor and stop doube posting your questions in more than one forum. I do not like having to answer the same question in 2 places and if I only answer one of them it makes it look like I didn't answer.