iCal failing to sync calendars with an Exchange 2010-based server - 'ical needs a valid email address'

Question

iCal (Version 5.0.1 (1547.4) - Mac OS X 10.7.2) is failing to sync calendar entries for an Exchange account setup via System Preferences.

While Mail and Address Book are able to send mail or sync to the server, the calendars show an exclamation mark next to the account name, which when clicked brings up the following dialogue sheet:

"ical needs a valid email address to connect to the exchange account"

Entering the email address of the account has no effect, and clicking the exclamation mark again simply re-opens the dialogue sheet.

Answer 1

Kudos to @jaberg for the hint, which let me get to the root of this.

This problem actualy related to my boss, who for some convoluted reason has two exchange accounts, one of which appears in the GAL, and one which does not.

The account that does not appear in the GAL was the one failing to sync with iCal - and lacking the power to fiddle with the GAL, I tried entering the email address of the first (GAL-listed) account into iCal. To my suprise, this allowed iCal to sync the calendar entries of the second account.

I still need to check for any side-effects of this hack - the whole thing seems to be bugs stacked on bugs - but we've got somewhere.

Answer 2

Have your Exchange Administrator check to make sure your account is on the GAL (Global Address List). There is an option to hide accounts that might be selected.

Answer 3

I found this problem was the Exchange password expiry.

If you log into the webmail version of exchange and get prompted to change your password performing this change will make your accounts work again