==== Required information ====
- iRedMail version (check /etc/iredmail-release):
- Linux/BSD distribution name and version:
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Web server (Apache or Nginx):
- Manage mail accounts with iRedAdmin-Pro?
- Related log if you're reporting an issue:
======== Required information ====
- iRedMail version-0.9.5-1

- Linux/BSD distribution name and version:
No LSB modules are available.
Distributor ID:    Debian
Description:    Debian GNU/Linux 8.4 (jessie)
Release:    8.4
Codename:    jessie

- Store mail accounts in which backend: mariadb
- Web server:  Nginx:
- Manage mail accounts with iRedAdmin-Pro?
- Related log if you're reporting an issue:
====

< Question > Continue? [y|N]y
[ INFO ] Installing package(s): postfix postfix-pcre mariadb-server mariadb-client postfix-mysql libdbd-mysql-perl php5-cli php5-json php5-gd php5-mcrypt php5-curl mcrypt php5-intl php5-mysql nginx-full php5-fpm dovecot-imapd dovecot-pop3d dovecot-lmtpd dovecot-managesieved dovecot-sieve dovecot-mysql amavisd-new libcrypt-openssl-rsa-perl libmail-dkim-perl clamav-freshclam clamav-daemon spamassassin altermime arj zoo nomarch cpio lzop cabextract p7zip rpm ripole libmail-spf-perl unrar-free pax python-sqlalchemy python-dnspython python-mysqldb python-jinja2 python-netifaces python-webpy python-beautifulsoup python-lxml uwsgi uwsgi-plugin-python python-bcrypt fail2ban bzip2 acl patch cron tofrodos logwatch unzip bsdutils
Reading package lists...
Building dependency tree...
Reading state information...
acl is already the newest version.
altermime is already the newest version.
altermime set to manually installed.
amavisd-new is already the newest version.
bzip2 is already the newest version.
cpio is already the newest version.
cron is already the newest version.
python-dnspython is already the newest version.
python-dnspython set to manually installed.
dovecot-imapd is already the newest version.
dovecot-lmtpd is already the newest version.
dovecot-managesieved is already the newest version.
dovecot-mysql is already the newest version.
dovecot-pop3d is already the newest version.
dovecot-sieve is already the newest version.
libcrypt-openssl-rsa-perl is already the newest version.
libcrypt-openssl-rsa-perl set to manually installed.
libmail-dkim-perl is already the newest version.
libmail-dkim-perl set to manually installed.
libmail-spf-perl is already the newest version.
libmail-spf-perl set to manually installed.
patch is already the newest version.
pax is already the newest version.
pax set to manually installed.
postfix is already the newest version.
postfix-mysql is already the newest version.
postfix-pcre is already the newest version.
ripole is already the newest version.
ripole set to manually installed.
spamassassin is already the newest version.
unzip is already the newest version.
unzip set to manually installed.
bsdutils is already the newest version.
mariadb-server is already the newest version.
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
mariadb-server : Depends: mariadb-server-10.1 (= 10.1.13+maria-1~jessie) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
<< ERROR >> Installation failed, please check the terminal output.
<< ERROR >> If you're not sure what the problem is, try to get help in iRedMail
<< ERROR >> forum: http://www.iredmail.org/forum/

how to fix?