We recently switched a customer from 1and1 hosted exchange email to our services.  The transition was smooth apart from one thing; Outlook for some reason kept prompting for the 1and1 account credentials.  We tried the following:

1. Calling the 1and1 helpdesk.  All they said was that deleting the exchange account on 1and1 would break the link.  I tried to reason that deleting the 1and1 account wouldn’t stop my computer trying to connect, however the conversation wasn’t going anywhere so I politely said thankyou.
2. Creating a new profile.
3. Disabling Outlook add-ins.  This is a great page describing various Outlook command line switches.
4. Deleting RSS feeds – we were concerned that RSS some caching of RSS may be connecting back to 1and1.
5. Re-booting the computer.
6. Re-installing Outlook.

No joy.  Next step was to find out what Outlook was trying to connect to.  We found fiddler which is a great utility that shows you all http traffic going in and out of your computer.

Installation was a snap.  Below were the requests of interest:

Fiddler http requests

Notice that the first two requests are to autodiscover.centella.co.uk and then it tries to connect to exchange.1and1.co.uk.

Autodiscover is a new facility in Outlook 2007, that helps configure Outlook clients.  It should just give up if there is no response – there is certainly no autodiscover credentials at autodiscover.centella.co.uk, so why does it try to go to exchange.1and1.co.uk?

John Savill wrote this article on how to force Microsoft Outlook to look at a particular autodiscovery server.

We checked the regsitry entry that John mentions in his post and in there was a link to an XML file which was redirecting requests to exchange.1and1.co.uk.  Bingo! Removing the key solved the problem and we no longer get the password prompt.  We can only assume that the XML file was created when the 1and1 hosted exchange account was setup.

Registry key pointing to file controlling auto discover

Regsitry Key value

Contents of XML file:

<?xml version="1.0" encoding="utf-8"?>
<Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/responseschema/2006">
    <Response xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a">
        <Account>
            <AccountType>email</AccountType>
            <Action>redirectUrl</Action>
            <RedirectUrl>https://Exchange.1and1.co.uk/autodiscover/autodiscover.xml</RedirectUrl>
        </Account>
    </Response>
</Autodiscover>