I am using openSUSE Tumbleweed on a reasonably fresh install.
I configured "mail server" through YaST2 and selected:
   [x] Enable virus scanning (AMaVIS)
   [x] Enable DKIM signing for outgoing mails

On completion I checked the running services and found an error in /var/log/mail as follows:

amavis[5656]: (!!)TROUBLE in pre_loop_hook: config: no rules were found!  Do you need to run 'sa-update'?
amavis[5656]: (!)_DIE: Suicide () TROUBLE in pre_loop_hook: config: no rules were found!  Do you need to run 'sa-update'?

and

clamd[8194]: Can't open file or directory

and

postfix/qmgr[12738]: warning: connect to transport private/amavis: Connection refused

and

amavis[14603]: (14603-01) (!)connect to /var/run/clamav/clamd-socket failed, attempt #1: Can't connect to a UNIX socket /var/run/clamav/clamd-socket: No such file or directory

and

amavis[14603]: (14603-01) (!)ClamAV-clamscan av-scanner FAILED: /usr/bin/clamscan unexpected exit 2, output="LibClamAV Error: cli_loaddbdir(): No supported database files found in /var/lib/clamav\nERROR: Can't open file or directory" at (eval 99) line 900.


Here is what I did to fix the errors:

(1) directory /var/run/clamav did not exist, so I created it
mkdir /var/run/clamav
chown vscan.vscan /var/run/clamav

(2) directory /var/lib/clamav was empty
an internet search suggested I should use the commands:
freshclam -v
sa-update

(3) freshclam -v 
worked ok, however, sa-update did not exist on my system.

Therefore...

(4) I installed the package "spamassassin" through YaST2 "software management" and then ran the command.

(5) sa-update

Note that a huge number of installs were triggered off by my selecting 
   [x] Enable virus scanning (AMaVIS)
in the first instance, but I assume that this one was missed. e.g. the package "perl-Mail-SpamAssassin" was already installed.

I also noted that in /etc/sysconfig/spamd the option "SPAM_SA_UPDATE" was set to "no", which I changed to "yes"

This may be a personal preference but internet consensus suggested it was a good thing to do.

Having made all these changes, I restarted the services and got a better outcome.

This suggests to me that the YaST2 configuration driven by the setting of
   [x] Enable virus scanning (AMaVIS)

requires all of those steps to be included in order to get the services running for the first time, and in the case of SPAM_SA_UPDATE=yes, keep it up-to-date.