I'm sorry, but what is this for a webmailserver?
We have everyday like 50 or more spam mail and we don't know where it comes from.
Also I want to check de email on my phone. Can't install it on any app (I have an Iphone)
Can someone explain to me why we get so much spam mail (and how to change it) and how I can install it on my phone?
Roundcube - it's just web-based mail program. Like outlook, thunderbird, iOS mail, gmail and etc.
You must check and tune your SMTP server for spam filters and etc.
For example install postgrey for postfix, do check DKIM,DMARK, SPF records for senders domain and mail hosts. Install spamassasin. Use black list from open source spam list projects.
About your phone. Ask your IT or provider about IMAP, SMTP settings of your mail server and config it on your phone.