My server doesn't send any email

[Bobses]

Hello again

My new server with CentOS 7 and Sentora doesn't want to send any email: neither when somebody comments to posts, nor after cron jobs.
The mail command doesn't work.

My postfix status:

Code:

systemctl status postfix
* postfix.service - Postfix Mail Transport Agent
  Loaded: loaded (/usr/lib/systemd/system/postfix.service; enabled; vendor preset: disabled)
  Active: active (running) since Fri 2016-12-30 20:35:14 EET; 21h ago
Main PID: 807 (master)
  CGroup: /system.slice/postfix.service
          |-  807 /usr/libexec/postfix/master -w
          |-  816 qmgr -l -t fifo -u
          |-23416 pickup -l -t fifo -u -o content_filter= -o receive_override_options=no_header_body_check...
          |-25878 smtpd -n smtp -t inet -u -o stress= -s 2
          |-25879 proxymap -t unix -u
          `-25880 anvil -l -t unix -u

Dec 31 17:53:45 s1 postfix/smtpd[25698]: lost connection after AUTH from unknown[91.200.12.139]
Dec 31 17:53:45 s1 postfix/smtpd[25698]: disconnect from unknown[91.200.12.139]
Dec 31 17:57:05 s1 postfix/anvil[25700]: statistics: max connection rate 1/60s for (smtp:2a05:91c0:505:...3:40
Dec 31 17:57:05 s1 postfix/anvil[25700]: statistics: max connection count 1 for (smtp:2a05:91c0:505::4e...3:40
Dec 31 17:57:05 s1 postfix/anvil[25700]: statistics: max cache size 2 at Dec 31 17:53:42
Dec 31 17:59:47 s1 postfix/smtpd[25878]: error: open database /etc/aliases.db: No such file or directory
Dec 31 17:59:47 s1 postfix/smtpd[25878]: connect from unknown[155.133.82.145]
Dec 31 17:59:50 s1 postfix/smtpd[25878]: warning: unknown[155.133.82.145]: SASL LOGIN authentication fa...cmQ6
Dec 31 17:59:50 s1 postfix/smtpd[25878]: lost connection after AUTH from unknown[155.133.82.145]
Dec 31 17:59:50 s1 postfix/smtpd[25878]: disconnect from unknown[155.133.82.145]
Hint: Some lines were ellipsized, use -l to show in full.

My dovecot status:

Code:

systemctl status dovecot
* dovecot.service - Dovecot IMAP/POP3 email server
  Loaded: loaded (/usr/lib/systemd/system/dovecot.service; enabled; vendor preset: disabled)
  Active: active (running) since Fri 2016-12-30 20:35:17 EET; 21h ago
Main PID: 1125 (dovecot)
  CGroup: /system.slice/dovecot.service
          |- 1125 /usr/sbin/dovecot -F
          |- 1127 dovecot/anvil
          |- 1128 dovecot/log
          |-25881 dovecot/auth
          |-25958 dovecot/auth -w
          `-25959 dovecot/config

Dec 30 20:35:17 s1 systemd[1]: Starting Dovecot IMAP/POP3 email server...
Dec 30 20:35:17 s1 systemd[1]: Started Dovecot IMAP/POP3 email server.

Also, in error_log I found:

Code:

sendmail: Cannot open mail:25

sendmail: RCPT TO:<*****@gmail.com> (454 4.7.1 <*****@gmail.com>: Relay access denied)

But the port 25 is open:

Code:

firewall-cmd --permanent --list-all
public
  target: default
  icmp-block-inversion: no
  interfaces: 
  sources: 
  services: dhcpv6-client dns ftp http https imap mysql ntp pop3 pop3s smtp smtps ssh
  ports: 25/tcp
  protocols: 
  masquerade: no
  forward-ports: 
  sourceports: 
  icmp-blocks: 
  rich rules: 

I really need help, but after the New Year's party.

I wish to all Sentora community a Happy New Year!