I too am having the same exact problem. I purchased and installed IREDMAIL PRO about a week ago. SpamAssassin never runs.
I added this, $sa_tag_level_deflt  = -100; to 50-user and every single message says:

X-Spam-Flag: NO
X-Spam-Score: 0
X-Spam-Level:
X-Spam-Status: No, score=x tests=[] autolearn=unavailable

I have never seen a reference to SpamAssassin once in any log or email header.

Watching thread.

Sorry for my late feedback.

The output from mysql command:
mysql> SELECT * FROM policy \G
*************************** 1. row ***************************
                          id: 1
                 policy_name: @.
                 virus_lover: N
                  spam_lover: Y
             unchecked_lover: NULL
          banned_files_lover: Y
            bad_header_lover: Y
         bypass_virus_checks: N
          bypass_spam_checks: N
        bypass_banned_checks: N
        bypass_header_checks: N
         virus_quarantine_to: virus-quarantine
          spam_quarantine_to: NULL
        banned_quarantine_to: NULL
     unchecked_quarantine_to: NULL
    bad_header_quarantine_to: NULL
         clean_quarantine_to: NULL
       archive_quarantine_to: NULL
              spam_tag_level: NULL
             spam_tag2_level: NULL
             spam_tag3_level: NULL
             spam_kill_level: NULL
       spam_dsn_cutoff_level: NULL
spam_quarantine_cutoff_level: NULL
        addr_extension_virus: NULL
         addr_extension_spam: NULL
       addr_extension_banned: NULL
   addr_extension_bad_header: NULL
              warnvirusrecip: NULL
             warnbannedrecip: NULL
               warnbadhrecip: NULL
              newvirus_admin: NULL
                 virus_admin: NULL
                banned_admin: NULL
            bad_header_admin: NULL
                  spam_admin: NULL
            spam_subject_tag: NULL
           spam_subject_tag2: NULL
           spam_subject_tag3: NULL
          message_size_limit: NULL
            banned_rulenames: NULL
          disclaimer_options: NULL
              forward_method: NULL
                 sa_userconf: NULL
                 sa_username: NULL
1 row in set (0.00 sec)

And syslog attached.

RichieX

*) Did you modify any Amavisd config files (/etc/amavis/conf.d/*)?
*) Please update value of SQL column "policy.policy_name='@.'" (in "amavisd" database) to -100, then try to send a testing email to trigger this issue, extract all log lines related to this new testing email and paste here for troubleshooting.

Don't worry, we will help you figure it out.

Finally, i figured it out and here's the solution:

*) Open file /etc/amavis/conf.d/50-user, find the last line in this file:

1;

*) Add 2 lines ABOVE the last line:

# controls running of anti-virus/spam code: 0 -> enabled, 1 -> disabled.
@bypass_virus_checks_maps = (0);
@bypass_spam_checks_maps  = (0);

*) Restart Amavisd service.

This issue happens on Ubuntu 18.04, not other linux/bsd distribution releases.

Spam check now working. Thanks @ZhangHuangbin.

Now i have error in maillog:

May 22 09:04:35 lxmail postfix/smtpd[20051]: disconnect from mail-lf0-f50.google.com[209.85.215.50] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
May 22 09:04:35 lxmail amavis[19927]: (19927-01) (!)connect to /var/run/clamav/clamd.ctl failed, attempt #1: Can't connect to a UNIX socket /var/run/clamav/clamd.ctl: No such file or directory
May 22 09:04:36 lxmail amavis[19927]: (19927-01) (!)connect to /var/run/clamav/clamd.ctl failed, attempt #1: Can't connect to a UNIX socket /var/run/clamav/clamd.ctl: No such file or directory
May 22 09:04:36 lxmail amavis[19927]: (19927-01) (!)clamav-socket: All attempts (1) failed connecting to /var/run/clamav/clamd.ctl, retrying (2)
May 22 09:04:42 lxmail amavis[19927]: (19927-01) (!)connect to /var/run/clamav/clamd.ctl failed, attempt #1: Can't connect to a UNIX socket /var/run/clamav/clamd.ctl: No such file or directory
May 22 09:04:42 lxmail amavis[19927]: (19927-01) (!)clamav-socket av-scanner FAILED: run_av error: Too many retries to talk to /var/run/clamav/clamd.ctl (All attempts (1) failed connecting to /var/run/clamav/clamd.ctl) at (eval 113) line 659.\n
May 22 09:04:42 lxmail amavis[19927]: (19927-01) (!)WARN: all primary virus scanners failed, considering backups

How can i solve this?

Both issues were fixed in the repacked iRedMail-0.9.8.