Enhancement/configuration options

[agimenez]

Hi @tersmitten, this is a branch where I've been doing some work to add further options that I have in my personal mail server. The main changes are the following:

• Manage master.cf as a template. This is a potentially breaking change, but there are some options that need to be set here (like enabling postscreen or the submission service, part of this patch series too). I'm open to add any additional guards (like a configuration boolean to enable the "take over" of this file), but I wanted this to be as simple as possible, and based on a Debian default configuration file.
• Add configuration to enable postscreen on port 25. The postscreen service provides additional protection against spam for SMTP service on port 25. Enabling this boolean will configure postscreen as well as some other services. A new configuration variable has been added to add DNSBL servers for postscreen.
• Add submission service. According to the RFC, port 25 should be only used by servers, and users should submit mail using the submission service (587).
• Add Dovecot SASL integration to enable client authentication using Dovecot SASL
• Add SPF policy agent so we can make SPF checks on incoming mail. Note that the policy agent configuration itself is not handled with this role, only the integration with Postfix, so that should be handled otherwise (I found https://github.com/mbocquet/spf, which I don't use -yet-, but it may be interesting to add some reference).

[agimenez]

Hi @tersmitten it seems that postfix is not starting in the tests, but the travis logs don't have any information. Is there any way to get the logs or the output of journalctl to troubleshoot?