I'm already with authsmtp like some of your customers like animoto ;-) Why doesn't Amazon provides such a functionnality. Authsmtp are really good (efficiency), but you can only get access to the last 200 messages for example and via a web interface. Not the best way to trace your problematic emails. Is it so dangerous for Amazon to solve such an issue? Any other solution to provide. I read in the AWS forums that somebody solve it with SPF, senderID approval from MS and DomainKeys set up. Is this really true and working?