I have just opened an old application with VS 2010 and it has converted it to .Net 4 but after it suggested that I use the ReplyToList property rather then the old ReplyTo property, I cannot get the application to build.
It keeps telling me that "'ReplyToList' is not a member of 'System.Net.Mail.MailMessage'". Intellisense offers me the ReplyToList collection and Add method without any problems so I do not understand why the build function is being so awkward.
Whether for some strange reason the IDE is using .Net 4 but the build is still trying to use .Net 2, I don't know. Is there any way I can check that?