Temporary stopping external incoming emails

[Frank Bonnet]

Hello

I would like to stop incoming/outgoing email to our site
without stopping internal emails exchange.

my configuration is quite classic


            INTERNET
                   |
                   |
           MX SERVER
                   |
                   |
       INTERNAL MAILHUB
                   |
                   |
        USERS'S MUAs

What I precisely wanted to do is :

 stop email flow between my mailhub and the MX server
 but not stop internal email service for our users.

Also I would like the MX server still accept incoming
emails from the Internet and keep them in its queue
to deliver later when I restart normal service.

Is it  feasible ?

Thanks a lot