passed (as an array), the message's data blocks would be allocated with a
refcount of 1, as though only one message header referenced the data. This
is really only an issue with bulkmail/multiple-recipient email and when the
first message was deleted, the remaining (headers) would point to free
data blocks which could and eventually would be overwritten by another
message's data (body text). chksmb would only catch the problem when the
refcount reached 0 but there was still one or more message headers pointing
at the data.