EPiServer Mail 4.3 to work with R2

While the development team is working on installer packages for EPiServer Community and EPiServer Mail for the new EPiServer Installation manager there are some workarounds that can be performed to run EPiServer Mail on R2.

Other than the normal instructions at:
http://world.episerver.com/en/Documentation/Items/Installation-Instructions/Create/Installation-Instructions---Create/

There’s a problem with the EPiServer Mail installer and that in R2 the UI folder is moved to: C:\Program Files\EPiServer\CMS\5.2.375.7\Application
<add virtualPath="~/SUI/" physicalPath="C:\Program Files\EPiServer\CMS\5.2.375.7\application\UI" name="UI" type="EPiServer.Web.Hosting.VirtualPathNonUnifiedProvider,EPiServer" />

You can copy that  folder back to your sites root and name it correctly and remove the Virtual path entry for the UI folder. If you want, after installation you can just copy the UI/Mail folder to the UI folder located in program files and add the virtual path again.

Also you will have to remove all entries to System.Web.Extensions 1.0 if you have that installed already, like:
<add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

<add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

Then add assembly redirect for 1.0 to 3.5:

<dependentAssembly xmlns="urn:schemas-microsoft-com:asm.v1">
<assemblyIdentity name="System.Web.Extensions" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0" />
</dependentAssembly>

<dependentAssembly xmlns="urn:schemas-microsoft-com:asm.v1">
<assemblyIdentity name="System.Web.Extensions.Design" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0" />
</dependentAssembly>

Edit:
You also need to make sure that you use full path to UI folder in site settings:
uiUrl="http://site/SUI/"