Update SMTP and SMTP_SSL docs for host/port

Author: Aniketsy

Doc/library/smtplib.rst

@@ -25,9 +25,9 @@ Protocol) and :rfc:`1869` (SMTP Service Extensions).
 
    An :class:`SMTP` instance encapsulates an SMTP connection.  It has methods
    that support a full repertoire of SMTP and ESMTP operations.
-   If *host* is omitted or set to an empty string, no connection is made during initialization; you must
-   call :meth:`connect` manually before using the instance.
-   If *port* is zero,the value of the :attr:`default_port` attribute is used.
+   If the host parameter is set to a truthy value, :meth:`connect(host, port)` is
+   called automatically when the object is created, otherwise :meth:`connect` must be
+   called manually.
 
    If specified, *local_hostname* is used as the FQDN of the local host in the HELO/EHLO
    command.  Otherwise, the local hostname is found using
@@ -64,6 +64,10 @@ Protocol) and :rfc:`1869` (SMTP Service Extensions).
       ``smtplib.SMTP.send`` with arguments ``self`` and ``data``,
       where ``data`` is the bytes about to be sent to the remote host.
 
+   .. attribute:: SMTP.default_port
+
+      The default port used for SMTP connections (25).
+
    .. versionchanged:: 3.3
       Support for the :keyword:`with` statement was added.
 
@@ -83,18 +87,20 @@ Protocol) and :rfc:`1869` (SMTP Service Extensions).
    An :class:`SMTP_SSL` instance behaves exactly the same as instances of
    :class:`SMTP`. :class:`SMTP_SSL` should be used for situations where SSL is
    required from the beginning of the connection and using :meth:`starttls` is
-   not appropriate. If the optional *host* and *port* parameters are given, the
-   SMTP_SSL :meth:`connect` method is called with those parameters during initialization.
-   If *host* is omitted or an empty string, no connection is made during initialization;
-   you must call :meth:`connect` manually before using the instance. If
-   *port* is zero, the standard SMTP-over-SSL port (465) is used.
+   not appropriate. If the host parameter is set to a truthy value,
+   :meth:`connect(host, port)` is called automatically when the object is created,
+   otherwise :meth:`connect` must be called manually.
 
    The optional arguments *local_hostname*, *timeout* and *source_address* have the same
    meaning as they do in the :class:`SMTP` class.  *context*, also optional,
    can contain a :class:`~ssl.SSLContext` and allows configuring various
    aspects of the secure connection.  Please read :ref:`ssl-security` for
    best practices.
 
+   .. attribute:: SMTP_SSL.default_port
+
+      The default port used for SMTP-over-SSL connections (465).
+
    .. versionchanged:: 3.3
       *context* was added.
 
@@ -256,6 +262,8 @@ An :class:`SMTP` instance has the following methods:
    2-tuple of the response code and message sent by the server in its
    connection response.
 
+   If the port is not specified, the value of the :attr:`default_port` attribute is used.
+
    .. audit-event:: smtplib.connect self,host,port smtplib.SMTP.connect