Suppressing unavailable imap server by default

[Michael Albinus]

Hi,

maybe it is a known technique, but even after RTFM I couldn't find it ...

I have configured an imap server which is reachable only sometimes (when
I have entered the company's lan). Connecting it via gnus takes always
~2 min, until there is a timeout, and the server is ignored ("denied" in
the *Server* buffer).

How could I change my configuration, that this timeout is reduced? Or
that prior to connecting the server via imap there is a check, whether
the server is reachable?

Extra bonus if I could configure it such a way that I don't need to
confirm that the server isn't reachable.

Thanks, and best regards, Michael.