What are people doing in relation to this?

Until now, I have been using postfix to send mail for client@clientsdomain to their real email address, but this fails for the reasons given when people unfortunate enough to use yahoo. com (or, more rarely, AOL) email them.

I could switch to running a mail server for them, rather than forwarding, but it involves them changing things. And it will be a pain for me.

I could collaborate with breaking RFCs and change the from: line of the header (is there an easy way to do that which ensures that there is a reply-to: line which adds the old from: if necessary?) but I don't really want to do that.

Or I could say 'tough, no more using client@clientsdomain', but they don't want that.

Ian