Cannot received email in RoundCube

[fantasymc]

After fresh install CentOS and Kloxo Mr, i have one problem with RoundCube.

Firstly, i can't send email because mail function disable, i already enable mail function and i can send email, it's maybe has risk for my vps?
Although i can send but i can't received email, how i find my problem?
This is 'sh /script/sysinfo'

A. Kloxo-MR: 6.5.0.f-2016111301

B. OS: CentOS release 6.9 (Final) x86_64

C. Apps:
   1. MySQL: mysql55-5.5.52-1.ius.el6.x86_64
   2. PHP: php-5.3.3-49.el6.x86_64
   3. Httpd: httpd-2.2.31-1.mr.el6.x86_64
   4. Lighttpd: --uninstalled--
   5. Nginx: --uninstalled--
   6. Qmail: qmail-toaster-1.03-1.3.38.mr.el6.x86_64
      - with: courier-imap-toaster-4.1.2-1.3.16.mr.el6.x86_64
   7. Dns: bind-9.9.9-1.mr.el6.x86_64

D. Php-type (for Httpd/proxy): suphp

Thanks you for your help.

[MRatWork]

Check your IP and domain in mxtoolbox.com.

[fantasymc]

Dear MRatWork,

i already solve my problem, i requested vendor check VPS and they fixed this, but they didn't tell me what problem.