Description of problem:
Custom server attribute outbound-socket-binding-ref is defined as required in XSD for mail subsystem but is shown and handled as not required in CLI.

Version-Release number of selected component (if applicable):
EAP 6.2.0.ER3

How reproducible:
Always

Steps to Reproduce:
1. Open jboss-eap-6.2/docs/schema/jboss-as-mail_1_1.xsd

2. See 
...
<xs:complexType name="custom-server-type" mixed="true">
.....
<xs:attribute name="outbound-socket-binding-ref" use="required" type="xs:string">
...

3. On default mail-session read operation description for adding new custom server
/subsystem=mail/mail-session=java\:jboss\/mail\/Default/custom=*:read-operation-description(name=add)

4. See ...
"request-properties" => {
            "outbound-socket-binding-ref" => {
                "type" => STRING,
                "description" => "Outbound Socket binding to mail server",
                "expressions-allowed" => true,
                "required" => false,
                "nillable" => true,
                "min-length" => 1L,
                "max-length" => 2147483647L
            },
....

Actual results:
value from XSD and that which CLI outputs differs


Expected results:
Synchronize XSD value with CLI - either make this attribute optional in XSD or required and not nillable in CLI.


Additional info:
I don't know how exactly parsing of config file is done, but when I edit standalone.xml and remove some required attribute (ie. outbound-socket-binding-ref of server smtp), it throws parsing exception after reload which is expectable. 
But it is not the case here, no parsing exception is thrown when I create custom server without attribute outbound-socket-binding-ref and reload, ie. it is handled also as not required.