Replace SSMTP with MSMTP for sendmail

- New parameter "SMTP_PORT"
- Removed parameter "SMTP_AUTH_METHOD"
- Replacing config mapping based on env-variables

Dockerfile-debian.template

@@ -9,7 +9,7 @@ RUN set -ex; \
         bzip2 \
         git \
 # For mail() support
-        ssmtp \
+        msmtp \
 # For tini installation
         gnupg dirmngr \
     ; \
@@ -108,7 +108,7 @@ RUN set -ex; \
     } > /usr/local/etc/php/conf.d/opcache-recommended.ini; \
     \
     { \
-        echo sendmail_path = "/usr/sbin/sendmail -t -i"; \
+        echo sendmail_path = "/usr/bin/msmtp -t"; \
     } > /usr/local/etc/php/conf.d/sendmail.ini; \
     \
     echo 'apc.enable_cli=1' >> /usr/local/etc/php/conf.d/docker-php-ext-apcu.ini; \