ZCML File
meta.zcml

<configure
    xmlns="http://namespaces.zope.org/zope"
    xmlns:meta="http://namespaces.zope.org/meta"
    >
<meta:directive
    namespace="http://namespaces.zope.org/mail"
    name="queuedDelivery"
    schema=".zcml.IQueuedDeliveryDirective"
    handler=".zcml.queuedDelivery"
    />
<meta:directive
    namespace="http://namespaces.zope.org/mail"
    name="directDelivery"
    schema=".zcml.IDirectDeliveryDirective"
    handler=".zcml.directDelivery"
    />
<meta:directive
    namespace="http://namespaces.zope.org/mail"
    name="smtpMailer"
    schema=".zcml.ISMTPMailerDirective"
    handler=".zcml.smtpMailer"
    />
</configure>