> Point where I was looking for is related to the new (1.8e) option to define
> the Sizelim= setting in K (Kb) or M (Mb) instead of amount of lines.
>
> 1st Q: I am wondering if this K or M setting is also possible for defining
> the digest size but can't find anything about that.

It is not documented for Digest. However, if you set something like:
Digest= Yes,Same,Daily,1900,Size(80k)
LISTSERV does not complain about the syntax. So you could try it and see
what happens.

> 2nd Q: a MIME digest contains more lines (headers etc.) as NOMIME digests.
> How does Listserv calculate this (in our case) 1500 limit? Calculated based
> on incoming?

LISTSERV will cut off at 1500 lines, regardless of what the lines
contain. So yes, it's the lines in the inbound messages to the digest.