I have heard that CLR integration is here to stay so that might be a something to consider.
If retrieving mail via POP3 is an option, create your own CLR stored procedure to read the mail. You could either write your own classes to handle the POP3 communication or use a third-party .NET library to simplify that part of it. Something like this for example: http://www.lesnikowski.com/mail/.
The assembly would likely need permissions set to EXTERNAL_ACCESS due to it using network resources.