Merge #1259

1259: Antivirus reject r=mergify[bot] a=micw

## What type of PR?

enhancement + documentation)

## What does this PR do?

- document behaviour if virus is detected
- add option to reject viruses in smtp dialogue

### Related issue(s)
- #1155

## Prerequistes

- [x] In case of feature or enhancement: documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.


Co-authored-by: Michael Wyraz <michael@wyraz.de>

core/rspamd/conf/antivirus.conf

@@ -4,5 +4,8 @@ clamav {
   symbol = "CLAM_VIRUS";
   type = "clamav";
   servers = "{{ ANTIVIRUS_ADDRESS }}";
+  {% if ANTIVIRUS_ACTION|default('discard') == 'reject' %}
+  action = "reject"
+  {% endif %}
 }
 {% endif %}

docs/configuration.rst

@@ -131,6 +131,13 @@ See the `python docs`_ for more information.
 
 .. _`python docs`: https://docs.python.org/3.6/library/logging.html#logging-levels
 
+Antivirus settings
+------------------
+
+The ``ANTIVIRUS_ACTION`` switches behaviour if a virus is detected. It defaults to 'discard',
+so any detected virus is silently discarded. If set to 'reject', rspamd is configured to reject
+virus mails during SMTP dialogue, so the sender will receive a reject message.
+
 Infrastructure settings
 -----------------------
 

towncrier/newsfragments/1259.feature

@@ -0,0 +1 @@
+Allow to reject virus mails by setting ANTIVITUS_ACTION=reject