I have 4 microsoft exchange accounts setup on my iPhone (as well as an iCloud mail account).
Since upgrading to iOS7 (and now 7.0.2), 1 of the 4 exchange accounts refuses to co-operate, giving a 'Cannot Get Mail, The Connection to the Server Failed' error.
I've deleted the account from the iPhone, and re-added it, and while everything seems okay when I add it (i.e. the little ticks appear when I set the account up), as soon as I go into the mail app, I get the error again.
Not sure why it's only having problems with that account, when the other 3 exchange accounts (all on the same domain, and setup in the same way) work perfectly okay still on iOS7.
The problem account also doesn't work on other iOS7 devices (iPhone/iPads), where I've also tried adding it, but still works perfectly okay on an iOS6 device.
I've also tried resetting my network settings, disconnecting and reconnecting to wi-fi, but still the problem persists.