Elaborated the documentation for the MailHost API somewhat.

lib/python/Products/MailHost/help/Mail-Host.stx

 MailHost: Sends mail through an SMTP server.
-  
+
   MailHosts allow you to send mail via the Simple Mail Transfer
   Protocol (SMTP).
 
-  This object can be used by the <dtml-sendmail> tag to handle
-  delivery of mail.
+  This object can be used deliver mail by the <dtml-sendmail> tag
+  or via the send() and simple_send() methods.
+
+    'send(messageText, mto=None, mfrom=None, subject=None, encode=None)'
+
+      Sends an email message where the messageText is an rfc822 formatted
+      message. This allows you complete control over the message headers,
+      including setting any extra headers such as Cc: and Bcc:.
+      The arguments are:
+
+        messageText -- The mail message. It can either be a rfc822
+        formed text with header fields, or just a body without any
+        header fields. The other arguments given will override the
+        header fields in the message, if they exist.
+
+        mto -- A commaseparated string or list of recipient(s) of the message.
+
+        mfrom -- The address of the message sender.
+
+        subject -- The subject of the message.
+
+        encode -- The rfc822 defined encoding of the message.  The
+        default of 'None' means no encoding is done.  Valid values
+        are 'base64', 'quoted-printable' and 'uuencode'.
+
+    'simple_send(self, mto, mfrom, subject, body)'
+
+      Sends a message. Only To:, From: and Subject: headers can be set.
+      The arguments are:
+
+        mto -- A commaseparated string or list of recipient(s) of the message.
+
+        mfrom -- The address of the message sender.
+
+        subject -- The subject of the message.
+
+        body -- The body of the message.
+

lib/python/Products/MailHost/help/MailHost.py

@@ -35,22 +35,38 @@ class MailHost:
     def send(messageText, mto=None, mfrom=None, subject=None,
              encode=None):
         """
-        Sends an email message.
+        Sends an email message where the messageText is an rfc822 formatted
+        message. This allows you complete control over the message headers,
+        including setting any extra headers such as Cc: and Bcc:.
         The arguments are:
 
-          messageText -- The mail message. It can either be a rfc822
-          formed text with header fields, or just a body without any
-          header fields. The other arguments given will override the
-          header fields in the message, if they exist.
+            messageText -- The mail message. It can either be a rfc822
+            formed text with header fields, or just a body without any
+            header fields. The other arguments given will override the
+            header fields in the message, if they exist.
 
-          mto -- A string or list of recipient(s) of the message.
+            mto -- A commaseparated string or list of recipient(s) of the message.
 
-          mfrom -- The address of the message sender.
+            mfrom -- The address of the message sender.
 
-          subject -- The subject of the message.
+            subject -- The subject of the message.
 
-          encode -- The rfc822 defined encoding of the message.  The
-          default of 'None' means no encoding is done.  Valid values
-          are 'base64', 'quoted-printable' and 'uuencode'.
+            encode -- The rfc822 defined encoding of the message.  The
+            default of 'None' means no encoding is done.  Valid values
+            are 'base64', 'quoted-printable' and 'uuencode'.
 
         """
+
+    def simple_send(self, mto, mfrom, subject, body):
+        """
+        Sends a message. Only To:, From: and Subject: headers can be set.
+        The arguments are:
+
+            mto -- A commaseparated string or list of recipient(s) of the message.
+
+            mfrom -- The address of the message sender.
+
+            subject -- The subject of the message.
+
+            body -- The body of the message.
+        """