$inbound = new \Mvdnbrk\Postmark\InboundMessage(file_get_contents('php://input'));

$inbound->from->name;                   // John Doe
$inbound->from->email;                  // john@example.com
$inbound->from->full;                   // John Doe <john@example.com>

$inbound->tag;
$inbound->replyTo;
$inbound->textBody;
$inbound->htmlBody;
$inbound->messageId;                    // MessageID assigned by Postmark.
$inbound->messageIdFromHeaders;         // Message-ID value from headers.
$inbound->strippedTextReply;
$inbound->originalRecipient;

$inbound->originalDate;                 // Wed, 6 Sep 2017 12:00:00 +0200
$inbound->date;                         // PostmarkDate::class which is an extension of the DateTime::class
$inbound->date->format('Y-m-d H:i:s')   // 2017-09-06 12:00:00
$inbound->date->isUtc                   // boolean, is the date in the UTC timezone?
$inbound->date->timezone;               // +02:00
$inbound->date->inUtcTimezone()         // Sets the timezone to UTC.
$inbound->subject;                      // Subject of the message.

$inbound->isSpam;                       // boolean, is the message to be considered as spam?
$inbound->spamStatus;                   // Spam status, defaults to 'No' when not present.
$inbound->spamScore;                    // float, defaults to 0.0 when not present.

$inbound->to->count()                   // Recipient count.
$inbound->cc->count()
$inbound->bcc->count()

$inbound->attachments->count()          // Attachment count.

$inbound->headers->count()              // Header count.

$inbound->to->each(function($contact) {
    $contact->name;
    $contact->email;
    $contact->full;
    $contact->mailboxHash;
});

$inbound->cc->each(function($contact) {
    $contact->name;
    ...
});

$inbound->bcc->each(function($contact) {
    $contact->name;
    ...
});

$inbound->attachments->each(function($attachment) {
    $attachment->name;
    $attachment->contentType;
    $attachment->contentLength;
    $attachment->content();         // Base64 decoded data
});

$inbound->attachments->first();

$inbound->attachments->last();

$inbound->headers->each(function($value, $key) {
    ...
});

$inbound->headers->get('Message-ID');
$inbound->headers->get('MIME-Version');
$inbound->headers->get('Received-SPF');
$inbound->headers->get('X-Spam-Score');
$inbound->headers->get('X-Spam-Status');
...