made postfix Alpine based

postfix/build.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/bash
+# docker login --username baloan --password 'yZBCUs5&@?:.'
+# docker run -d --name apache -p80:80 -v/root/kopano/dist:/var/www httpd
+export DOCKER_BUILDKIT=1
+docker build -t postfix .
+# docker container prune -f
+# docker run -d --name postfix postfix 
+# docker exec -it postfix bash
+# docker stop postfix
+# docker rm postfix