Hi Matthias,
What version of mojoPortal?
Very old versions of mojoPortal used the <system.net section smtp settings in Web.config for password recovery but newer versions use the user.config settings.
Unless you have this as true:
<add key="EnableSiteSettingsSmtpSettings" value="true" />
if that is true then it ignores other user.config settings and smtp settings come from the Site Settings page, so you may need to check there.
Hope that helps,
Joe