Can somebody help me please ?
Yes, but you need to start by getting a far better understanding of running your own server and domain.
From the limited amount of data you provide in this thread I get the impression you are willing to run a mailserver at your home connection, this is perfectly possible, but nor for the domain of your provider (casema.nl), they already run a mail server for that domain on which your mail is received.
SME Server has a internal mailserver that is capable of handling mail for domains, but you will need to have your own domain name, which is also a valid domain name, domains ending in .local are not a valid domain, domains ending on .nl for instance are.
To fetch your casema.nl mail for your casema hosted e-mailaddress you should just configure your local mail client as you normally do and make sure that SMTP proxy (in the e-mail settings tab on your server manager) on your server is disabled, that way you should be able to have your mail client reach the casema.nl mail server to collect your mail.
If you really want to inject the mail form your casema.nl account into a local account on your SME Server you can use the fetchmail contrib that you can find in the wiki, but I doubt that is what you are after since you do not have a valid domain from which you can send mail.