Added ssmtp for outgoing mail

Dockerfile

@@ -4,8 +4,9 @@
 FROM wordpress:4.9.2-fpm
 
 RUN apt-get update \
-	&& apt-get install -y openssh-server \
-	&& useradd -c "Hosting Admin User" -u 1000 -g users -G www-data -d /var/www/html -M lamp
+	&& apt-get install -y openssh-server ssmtp \
+	&& useradd -c "Hosting Admin User" -u 1000 -g users -G www-data -d /var/www/html -M lamp \
+	&& sed -i -e 's/^mailhub=mail$/mailhub=smtp/' -e "s/${HOSTNAME}//" /etc/ssmtp/ssmtp.conf
 
 COPY sshd_config.patch /tmp
 RUN (cd / && patch -p0 ) < /tmp/sshd_config.patch && rm /tmp/sshd_config.patch