Hi,
there's an RFC covering smarthosts now, 2476. It hasn't been very widely
deployed, but IMO no good MUA can be blatantly incompatible with it.
RFC 2476 doesn't suggest that the message submission servers hould remove bcc.
For this reason, I think that a MUA which wants bcc removed cannot trust
the smarthost to do so. It must do the job itself.
Philip Hazel writes:
4. Among the MUAs, I think that Pine never sends Bcc: lines, but Mutt by
default does, assuming that the MTA will deal with them (Mutt does
not use the -t option).
IMNSHO, mutt is in the wrong.
Whether exim is right is a different question. I guess that boils down
to whether you prefer to Do Things Right or add workarounds for
brokenware.
Arnt