What does the message mean ? Is Smtp no more supported ?
No. You can clearly see in the message that it came from an IMAP server, not an SMTP server. You connected to the wrong IP:port.
I have nearly the same with pop3send, but I can use Imap with ssl and the same credentials to get emails.
POP3, IMAP, SMTP - they are different protocols, and require different components to access them properly.
I have read that we could send emails with imap moving messages in the outbox folder.
Nope. IMAP is a mailbox management protocol. It can only manage the content of mailboxes/folders, nothing more. It does not support sending emails in any way. SMTP is the only official way to send emails.
But how can we set mailto and mailfrom ?
You don't, because sending emails is not part of IMAP, only SMTP.