Mail error:cannot use!

I have these error :
[root@dwizhosting log]# vi maillog.1
Apr 22 23:59:02 dwizhosting postfix/postfix-script: starting the Postfix mail system
Apr 22 23:59:02 dwizhosting postfix/master[18549]: daemon started -- version 2.2.2, configuration /etc/postfix
Apr 23 01:07:07 dwizhosting pop3-login: Login: web2_support [::ffff:127.0.0.1]
Apr 23 01:07:14 dwizhosting pop3-login: Login: web2_support [::ffff:127.0.0.1]
Apr 23 01:45:49 dwizhosting postfix/smtpd[22201]: warning: cannot get certificate from file /etc/postfix/ssl/smtpd.crt
Apr 23 01:45:49 dwizhosting postfix/smtpd[22201]: warning: TLS library problem: 22201:error:02001002:system library:fopen:No such file or directory:bss_file.c:278:fopen('/etc/postfix/ssl/smtpd.crt','r'):
Apr 23 01:45:49 dwizhosting postfix/smtpd[22201]: warning: TLS library problem: 22201:error:20074002:BIO routines:FILE_CTRL:system lib:bss_file.c:280:
Apr 23 01:45:49 dwizhosting postfix/smtpd[22201]: warning: TLS library problem: 22201:error:140DC002:SSL routines:SSL_CTX_use_certificate_chain_file:system lib:ssl_rsa.c:760:
Apr 23 01:45:49 dwizhosting postfix/smtpd[22201]: cannot load RSA certificate and key data
Apr 23 01:45:50 dwizhosting postfix/smtpd[22201]: connect from fr5.webmaillogin.com[216.40.35.69]
Apr 23 01:45:51 dwizhosting postfix/smtpd[22201]: 72EC010E841B: client=fr5.webmaillogin.com[216.40.35.69]
Apr 23 01:45:52 dwizhosting postfix/cleanup[22211]: 72EC010E841B: message-id=<[email protected]>
Apr 23 01:45:53 dwizhosting postfix/qmgr[18555]: 72EC010E841B: from=<[email protected]>, size=99584, nrcpt=1 (queue active)
Apr 23 01:45:53 dwizhosting sendmail[22217]: k3MIjrLd022217: from=putty, size=110, class=0, nrcpts=1, msgid=<[email protected]>, relay=putty@localhost
Apr 23 01:45:53 dwizhosting postfix/smtpd[22225]: warning: cannot get certificate from file /etc/postfix/ssl/smtpd.crt
Apr 23 01:45:53 dwizhosting postfix/smtpd[22225]: warning: TLS library problem: 22225:error:02001002:system library:fopen:No such file or directory:bss_file.c:278:fopen('/etc/postfix/ssl/smtpd.crt','r'):
Apr 23 01:45:53 dwizhosting postfix/smtpd[22225]: warning: TLS library problem: 22225:error:20074002:BIO routines:FILE_CTRL:system lib:bss_file.c:280:
Apr 23 01:45:53 dwizhosting postfix/smtpd[22225]: warning: TLS library problem: 22225:error:140DC002:SSL routines:SSL_CTX_use_certificate_chain_file:system lib:ssl_rsa.c:760:

Please tell me to fix this problem.(I cannot use mail .)

 

another mail error

[root@dwizhosting log]# vi maillog
Apr 26 09:04:15 dwizhosting postfix/master[30142]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling
Apr 26 09:04:15 dwizhosting postfix/master[30142]: warning: process /usr/libexec/postfix/pickup pid 3469 exit status 1
Apr 26 09:04:15 dwizhosting postfix/master[30142]: warning: /usr/libexec/postfix/pickup: bad command startup -- throttling
Apr 26 09:05:02 dwizhosting sendmail[3277]: k3Q202vk003277: timeout waiting for input from [127.0.0.1] during client greeting
Apr 26 09:05:02 dwizhosting sendmail[3277]: k3Q202vk003277: to=root@localhost, ctladdr=root (0/0), delay=00:05:00, xdelay=00:05:00, mailer=relay, pri=30165, relay=[127.0.0.1] [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection timed out with [127.0.0.1]
Apr 26 09:05:03 dwizhosting sendmail[3282]: k3Q203Jm003282: timeout waiting for input from [127.0.0.1] during client greeting
Apr 26 09:05:03 dwizhosting sendmail[3282]: k3Q203Jm003282: to=root, ctladdr=root (0/0), delay=00:05:00, xdelay=00:05:00, mailer=relay, pri=30285, relay=[127.0.0.1] [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection timed out with [127.0.0.1]
Apr 26 09:05:15 dwizhosting postfix/smtpd[3506]: fatal: file /etc/postfix/main.cf: parameter setgid_group: unknown group name: postdrop
Apr 26 09:05:15 dwizhosting postfix/pickup[3507]: fatal: file /etc/postfix/main.cf: parameter setgid_group: unknown group name: postdrop
Apr 26 09:05:16 dwizhosting postfix/master[30142]: warning: process /usr/libexec/postfix/smtpd pid 3506 exit status 1
Apr 26 09:05:16 dwizhosting postfix/master[30142]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling
Apr 26 09:05:16 dwizhosting postfix/master[30142]: warning: process /usr/libexec/postfix/pickup pid 3507 exit status 1
Apr 26 09:05:16 dwizhosting postfix/master[30142]: warning: /usr/libexec/postfix/pickup: bad command startup -- throttling

 

Yes, I use.I plan to re-install ispconfig but I found new error:httpd bad group name apache.

[root@dwizhosting etc]# service httpd start
Starting httpd: httpd: bad group name apache

Is this a apache's problem?

 

Which tutorial did you use to set up your server?
Which distribution do you use?