When Anonymous is Not Enough

A couple of weeks ago I was re-installing SharePoint at a client's and posted about problems with incoming email. Today I found a new interesting thing in SharePoint. I got an email from the client that when they tried to click on the Sign In link for one of the sites, they were getting a '401 Unauthorized' error and not getting prompted to login like they should. So I took a look and they were right, no prompt, just an error.

So I looked into the IIS web application settings and made sure that anonymous access was checked. Everything looked ok to me so I started searching on the web for information but really couldn't find anyone that was having the same type of problem. I decided to look at the settings on another SharePoint install that was anonymous but allowed users to log into the site if they needed to. When I looked at the settings for that Web application, I noticed that the anonymous and authenticated checkboxes were both checked, so I tried that on the clients site. BAM! The site was now prompting for user logins and passwords when you click on the sign in link.

I was surprised that the settings for this Web application were not correct because I used SharePoint to turn on anonymous access. Just another thing to add to the list of things you may need to check when something is a little flaky in SharePoint.