Document the new mail and Schleuder services (refs: #16121)

wiki/src/contribute/working_together/roles/sysadmins.mdwn

@@ -313,6 +313,16 @@ Below, importance level is evaluated based on:
   - [[sysadmins/automated_tests_in_Jenkins]]
 * importance: critical (as a key component of our development process)
 
+## Mail
+
+* purpose: handle incoming and outgoing email for some of our
+  [[Schleuder lists|sysadmins#schleuder]]
+* access: public MTA listening on `mail.tails.boum.org`
+* tools: [[!debpts postfix]], [[!debpts amavisd-new]], [[!debpts spamassassin]]
+* configuration: `tails::postfix`, `tails::amavisd_new` and
+  `tails::spamassassin` classes in [[!tails_gitweb_repo puppet-tails]]
+* importance: high (at least because WhisperBack bug reports go through this MTA)
+
 <a id="mumble"></a>
 
 ## Mumble
@@ -340,6 +350,17 @@ Below, importance level is evaluated based on:
     Puppet module
 * importance: critical (needed to release Tails)
 
+<a id="schleuder"></a>
+
+## Schleuder
+
+* purpose: host some of our Schleuder mailing lists
+* access: anyone can send email to these lists
+* tools: [[!debpts schleuder]]
+* configuration: `tails::schleuder` class in [[!tails_gitweb_repo
+  puppet-tails]]
+* importance: high (at least because WhisperBack bug reports go through this service)
+
 ## Tor bridge
 
 * purpose: provide a Tor bridge that Tails contributors can easily use