It appears that there is an issue with the return path in the email headers for forum email updates. I had switched on the option in my email server to validate envolpes and I stopped getting email updates to forums or threads I had subscibed to.

This used to work OK when the email was coming from flyertalk.com but now that email is coming from internetbrands.com it doesn't work.

This isn't a happy situation as turning off envelope validation allows from spam through.

Can someone look into this?