Understanding my network

[Arthur Dent]

Hello all,

I am part-way through a bare-metal rebuild of my small home server (it
was F15, I am rebuilding as F17). This machine serves up my IMAP mail
with Dovecot and Squirrelmail and hosts my small (mainly static)
website.

The machine in question sits on my home network at 192.168.2.2. I have
opened port 993 on the firewall. I have a domain name (let's call it
example.org) with dyndns.org which points to my IP address (let's call
that 123.456.789.123) and my router forwards port 993 to 192.168.2.2.

So here's the thing - and I don't remember having this problem with F15
(or previous):
I can access my mail using a client on another machine in my network if
I configure it to use 192.168.2.2, but for my mobile devices I configure
the email client to point to example.org. If I am outside of my network
they can access mail fine, but if I am at home and they are connecting
via my own wi-fi... no joy...

The same by the way is true of SSH. Although I use a non-standard port
for SSH the principle is the same.

I have obviously messed up or missed out some configuration step, but I
can't understand where I have gone wrong.

Can anyone help me to fix this?

Thanks

Mark