1. After install, in admin panel I see this warning all the time (See attachment 1)
I cheked API key - everything done...
2. After checking how sending mail from my site work, I have warnig from Joomla! (See attachment 2)
Can anybody help me please?
When we created the cmandrill extension mandrill didn't have support for emails that had cc . That is why we are sending through phpmailer. You should actually not see this warning as it should go into the error log and it should not be shown to the user.
Set error reporting in your global config to none and make sure that debug is also turned off.
Currently mandrill is supporting mails with CC and we should address this in the next update.