Chris Bolton:I don't use SPF but am frustrated by the way it has broken what used to be a useful forwarding service I provided for a local charity.
Is there any chance that Mercury could include Sender Rewriting Scheme (SRS) as way to fix this problem?
Or does anyone know if it would be hard to write a daemon to do this?
You've found one of the main weaknesses of SPF and why it has never really caught on.
Is it the charity's outgoing mail that can't use forwarding? If so you may be able to change their SPF records to help. If it is incoming mail that you are forwarding on to personal mailboxes, then there's not much you can do. :(
In a similar situation I set up POP boxes for the people to download.