Set in place web based email archive viewer for system emails

[renoirb]

Set in place Lurker, a web based email archive viewer, so we can read system emails from a web browser. Idea is to make monit and error messages to be sent through SMTP in a more reasonable rate.

Tasks

• Configure Postfix master.cnf to add a content filter and add to lurker index
• Ensure Postfix content filter lets the mail go
• Ensure lurker can sort emails (monit in one box, cron in another, etc)

Review

• Keep lurker, or use MailDrop

[renoirb]

Something is in place on staging while working on #119 but was enabled only for staging. This task is to have it also in production.

[renoirb]

At this time lurker is configured to send everything in one archive, there should be work to add filtering.

[renoirb]

Could be done also while working on:

• Setup a mailbox w/ POP3 access for Discourse to use #161
• Configure system emails to be saved on mail node, make logstash read through IMAP plugin #127