[
  {
    "header": "<1234@local.machine.example>\n",
    "expected": [
      "1234@local.machine.example"
    ]
  },
  {
    "header": "<1234@local.machine.example> <3456@example.net>\n",
    "expected": [
      "1234@local.machine.example",
      "3456@example.net"
    ]
  },
  {
    "header": "<1234@local.machine.example>\n <3456@example.net> \n",
    "expected": [
      "1234@local.machine.example",
      "3456@example.net"
    ]
  },
  {
    "header": "<1234@local.machine.example>\n\n <3456@example.net>\n",
    "expected": [
      "1234@local.machine.example"
    ]
  },
  {
    "header": "              <testabcd.1234@silly.test>  \n",
    "expected": [
      "testabcd.1234@silly.test"
    ]
  },
  {
    "header": "<5678.21-Nov-1997@example.com>\n",
    "expected": [
      "5678.21-Nov-1997@example.com"
    ]
  },
  {
    "header": "<1234   @   local(blah)  .machine .example>\n",
    "expected": [
      "1234   @   local(blah)  .machine .example"
    ]
  },
  {
    "header": "<>\n",
    "expected": null
  },
  {
    "header": "malformed@id.machine.example\n",
    "expected": [
      "malformed@id.machine.example"
    ]
  },
  {
    "header": "   malformed2@id.machine.example \t  \n",
    "expected": [
      "malformed2@id.machine.example"
    ]
  },
  {
    "header": "   m \n",
    "expected": [
      "m"
    ]
  }
]