From time to time pop3 server refuses connection telling kmail that password is wrong. This makes kmail asking me for the new password. Is there any way for kmail to ignore such server responses and try again to check for new mails?

Unfortunately this is probably a case where Kontact/KMail's following of what the email server has is likely not going to help you here. As far as I am aware, you can't disable this behaviour. I think it does pre-fill the password dialog though, so hitting enter should cause it to use the currently entered password again.