Microsoft Azure is currently under CTP (Community Technical Preview)

During this period, you can use their service for free. This tutorial walks you through how to get a free account so that you can store your email attachments for free.

First, go register for the CTP by clicking on the "Register for Services" link as shown below. You will have to use your Windows Live ID to sign in.

Click "Continue" to register on Microsoft Connect, accept the "Terms of Use".

Register your name and contact information as shown below.

Now that you are registered on Microsoft Connect, you can apply to a Connect program.

You will be prompted for more information in order to register for Azure.

If you see the following screen, your registration has succeeded.

Now, all you need to do is sit back and wait for the invitation code from Microsoft Connect website. You should first receive the invitation code for Microsoft .Net Services and Microsoft SQL Services usually within the first couple of days. You do not need them, so you can ignore for now. The invitation code for Windows Azure can take some time, depending on how quickly Microsoft can provision for more capacity. For us, it took 10 days. Yours may be more. Once you receive the Azure invitation code, you can sign up for an Azure account by redeeming your invitation token. 

Once your account is activated, you will be logged into the Azure Services Developer Portal. From there, you can start new projects. You need to setup a Storage Account. You will need the storage account name and the "Primary Access Key", and put them in the Outlook->Options->Attachment Manager Azure configuration page. In the example below, the account name is "outlookcloud". It is the first word in the Endpoints shown below (e.g., http://outlookcloud.blob.core.windows.net)

Congratulations! You are done. You can enjoy 50GB storage and 20GB/day storage bandwidth, all for free. Each Azure account can provision 2 storage projects, so if you need it, you can double that quota.