Probably, I should've done it line by line to avoid a mess in my post. So here I'll try to categorize the DNS parameters.
Since I can't edit my post...
1) In A record there's a SUBDOMAIN box where I just put @ sign (it means root, right?), then there's a default TTL 7200, and IP ADDRESS when I put my static IP.
2) The next line is CNAME record and in SUBDOMAIN box I put www and then 7200 TTL and then the HOST NAME where I just typed mydomain.com
3) The next line is A record for a mail server. In SUBDOMAIN box I have smtp, then TTL 7200 and finally IP ADDRESS.
4) And the last line is MX record. In SUBDOMAIN I have smtp, then TTL 7200 and then PREFERENCE 1 and the last thing is HOST where I have my domain.com
Are those parameters correct?