The returned header value (as returned by a call to {@see \ReceivedHeader::getValue()}) for a
ReceivedHeader is the same as the raw value (as returned by a call to
{@see \ReceivedHeader::getRawValue()}) since the header doesn't have a single
'value' to consider 'the value'.

The parsed parts of a Received header can be accessed as parameters. To
check if a part exists, call {@see \ReceivedHeader::hasParameter()} with the
name of the part, for example: `php $header->hasParameter('from') ` or

by calling {@see \ReceivedHeader::getValueFor()}, for example
```php $header->getValueFor('with'); ```.

Additional parsing is performed on the "FROM" and "BY" parts of a received
header in an attempt to extract the self-identified name of the server, its
hostname, and its address (depending on what's included).  These can be
accessed directly from the ReceivedHeader object by calling one of the
following methods:

o {@see \ReceivedHeader::getFromName()} -- the name portion of the FROM part
o {@see \ReceivedHeader::getFromHostname()} -- the hostname of the FROM part
o {@see \ReceivedHeader::getFromAddress()} -- the adddress portion of the FROM
  part
o {@see \ReceivedHeader::getByName()} -- same as getFromName, but for the BY
  part, and etc... below
o {@see \ReceivedHeader::getByHostname()}
o {@see \ReceivedHeader::getByAddress()}

The parsed parts of the FROM and BY parts are determined as follows:

o Anything outside and before a parenthesized expression is considered "the
  name", for example "FROM AlainDeBotton", "AlainDeBotton" would be the name,
  but also if the name is an address, but exists outside the parenthesized
  expression, it's still considered "the name".  For example:
  "From [1.2.3.4]", getFromName would return "[1.2.3.4]".
o A parenthesized expression MUST match what looks like either a domain name
  on its own, or a domain name and an address.  Otherwise the parenthesized
  expression is considered a comment, and not parsed into hostname and
  address.  The rules are defined loosely because many implementations differ
  in how strictly they follow the standard.  For a domain, it's enough that
  the expression starts with any alphanumeric character and contains at least
  one '.', followed by any number of '.', '-' and alphanumeric characters.
  The address portion must be surrounded in square brackets, and contain any
  sequence of '.', ':', numbers, and characters 'a' through 'f'.  In addition
  the string 'ipv6' may start the expression (for instance, '[ipv6:::1]'
  would be valid).  A port number may also be considered valid as part of the
  address, for example: [1.2.3.4:3231].  No additional validation on the
  address is done, and so an invalid address such as '....' could be
  returned, so users using the 'address' header are encouraged to validate it
  before using it.  The square brackets are parsed out of the returned
  address, so the value returned by getFromAddress() would be "2.2.2.2", not
  "[2.2.2.2]".

The date/time stamp can be accessed as a DateTime object by calling
{@see \ReceivedHeader::getDateTime()}.

Parsed comments can be accessed by calling {@see \ReceivedHeader::getComments()}.  Some implementations may include connection
encryption information or other details in non-standardized comments.