JMS - OpenJMS

[Chiappone]

Hi,

I'm creating a project that uses OpenJMS as the way to exchange
information between the applications.
The kind of queue I'll use is the topic, publish/subscribe.
Building an example, I got the following "issue":

The publisher publishes a message. All the subscribers gots the message
properly.
The publisher send another message. All the subscribers gets this
message AND the first sent one. As follows.

Subscriber1 Subscriber2
--- First delivery
Message1 Message1
--- Second delivery
Message1 Message1
Message2 Message2
---- Third delivery
Message1 Message1
Message2 Message2
Message3 Message3

Why?
Is it related to durable subscribers implementation?
I have not done anything in this project that refers to this kind of
implementation. Plus, all the documentation that I found on the
internet is about to implementing durable subscribers, what brings me
to think that the default implementation is the non-durable
subscription.

Can anyone help me?

Don't worry if you don't understand something I said here. My english
is not as perfect as it was suposed to be. Ask me if you don't
understand something, please .

Thank you all.