Update firststeps-disable_ipv6.en.md

nginx, dovecot and php-fpm config files fixes

docs/post_installation/firststeps-disable_ipv6.en.md

@@ -80,4 +80,17 @@ Restart Postfix:
 
 ```
 docker compose restart postfix-mailcow
-```
+```
+
+**5.** if your docker daemon completly disable ipv6 
+
+fix nginx, dovecot and php-fpm config files too
+
+```
+sed -i '/::/d' data/conf/nginx/listen_*
+sed -i '/::/d' data/conf/nginx/templates/listen*
+sed -i 's/,\[::\]//g' data/conf/dovecot/dovecot.conf
+sed -i 's/\[::\]://g' data/conf/nginx/dynmaps.conf
+sed -i 's/\[::\]://g' data/conf/phpfpm/php-fpm.d/pools.conf
+```
+