iphone: Microsoft Exchange e-mail account (Hong Kong)

Hi,
does anyone experience connection problems to an exchange mail server on the iphone or another ios device? Since last Thursday, I'm unable to connect to exchange. Server is in Germany. I'm wondering if it is an expat-problem or not...

Error message: "Unable to verify account information".

Our IT team in Germany says they haven't changed any settings. Connection worked without any problems for three years (!), now it doesn't work at all.
Tried several fixes, including deleting the account, setting it up again and a patch that should extend the timeout... Nothing worked so far. It doesn't seem to be device-related because I tried setting up the account on my ipad, too (never used exchange on that device), doesn't work...
Thanks for any hints

Dominik