Hello Ben Parker,

> >Is it possible to add a serial number to the mails,

> This is automatically done with Digests, but not with single messages.

In former times we had a serial number in the subject line of single
messages but that was not useful as it makes threading impossible
with the simple widespread mail programmes.


> >e.g. by inserting a header line "X-Number: ..." ?

> There is no such header line so this won't work.

Where are the possible "X-..."-headers listed?

Do you have any other suggestions how to check whether each list
members gets every single mail?

Thank you
Erwin