digraph architecture {

  subgraph cluster_0 {
    style=filled;
    color="#d3d7cf";
    label = "Local network";
    node [style=filled,fillcolor=white];

    reverseproxy  [shape=box];
    social        [shape=box];
    email         [shape=box];
    integration   [shape=box];
    database      [shape=box];

    reverseproxy -> social    [label="HTTP"];
    social -> integration     [label="HTTP"];
    social -> database        [label="PostgreSQL (5432)"];
    integration -> database   [label="PostgreSQL (5432)"];
    email -> integration      [label="SMTP"];

  }

  internet  -> reverseproxy   [label="HTTP"];
  internet  -> email          [label="SMTP"];
  email     -> internet       [label="SMTP"];

}