PowerMTA Server Not starting

Question

I have recently installed PowerMTA server on CentOS 6, every prerequisite was installed according to Document and License was entered in correctly configuration file was also correctly setup in /etc/pmta/config but unable to start pmta service and getting this error in logs,

[root@mail ~]# pmtad --debug
    Host names: mail.fFd3EDBc6dDfcbe1Bac1.com [127.0.0.1] [x.x.x.x] localhost.ec2.internal localhost
    Domain suffix: ec2.internal
    Name servers: x.y.z.z
    SMTP source IP addresses:
        virtual MTA "{default}": (any local)
        virtual MTA "vmta_d_13541_x.x.x.x": x.x.x.x
    Domain Keys:
    OS: Linux 2.6.32-696.16.1.el6.x86_64 (CentOS release 6.9 (Final))
    glibc v2.12 (stable), NPTL 2.12
    OpenSSL 1.0.0i 19 Apr 2012
    1/1 CPU (x86_64; Intel Xeon CPU E5-2676 v3 @ 2.40GHz)
    1024 MB memory detected
    Priority nice range: min. 15, max. 0
    Use of realtime priorities disabled
    Max. opened files: 4096, max. threads: infinite
    Max. virtual memory: unlimited, max. data size: unlimited
    Using license key Elysium3-5-316904
    Spool initialization starting
    Spool /var/spool/pmta
        0 files, 0 directories, nextDir=0
    Total of 0 files in use
    Maximum number of recipients (based on system resources): 768000
    Running under user pmta (uid 497); group pmta (gid 496)
    Resolver: multi, 4 dispatchers
    Resources allow for at most 0 pipe delivery thread(s)
    Open file limit (ulimit -H -n) too low (4086), need at least 7767
    SMTP Listener at x.x.x.x:2025 starting
    SMTP Listener at x.x.x.x:2025 stopped
    Stopping remaining threads...
    Startup error: Insufficient process resources

sysctl.conf is set to 99999