Re: [exim] unseen and headers_add

> A) Use the acl_m variables.
> They accompany the message they are born with and can be read, but not (yet)
> modified in the routers and transports.

Can you say a little more about how you differentiate between the unseen and original addresses when you use this technique? (I
understand the part about using an acl_m later on. It's the conditional setting of it that I'm a little hazy on.)

> B) AFAIK, that part of the spec applies only to headers added/modified during
> the delivery process. We modify 'Subject:' and add headers in DATA acl's that
> traverse as many a 4 chained 'unseen' routers without loss or alteration.

Could be so. I have found through experimentation that if the original and the unseen address end up at the same transport, the
header modifications are gone. If they end up at different transports, the header modifications on the unseen address sticks.
Based on the wording of the spec, it seems like the second, apparently successful, case might be unintentional anyhow.