any MQ services based on email?

I am looking for MQ systems (rabbitmq , activemq) for our programs. Almost all MQ run o开发者_运维问答n ports. I was wondering if there are any MQ systems running on smtp or email services.

Basically I am trying to avoid the hassle of setting up a new software and opening up ports in different firewalls (its a hassle).

RabbitMQ is designed from the ground up to interoperate with other messaging systems: it is the leading implementation of AMQP, the open standard for business messaging, and, through adapters, supports XMPP, SMTP, STOMP and HTTP for lightweight web messaging.

supports SMTP? from: http://www.rabbitmq.com/