> Hi,
> Can one mailing be sent out to multiple lists on listserv by placing all
> the different list addresses in the TO: line?

Yes. However, there is a limit to the number of lists you can send an
identical message without triggering the Spam Filter in LISTSERV®

> We've tried it here and it
> doesn't seem to like a space delimiter or at least I think thats the issue.

Most mail clients use a comma delimiter.

>  Should the delimiter be a comma/semi colon or is it not possible to do
> this in one shot?

Comma, e.g....
To:  [log in to unmask], [log in to unmask], [log in to unmask], [log in to unmask]

Again, if you use too many lists, LISTSERV will reject them, even if you
send them
separately. If this happens, you will need to create a "Super list" and
make all these lists "Sub lists" of the Super list. Now you just send 1
message to the Super list which in turn is distributed to all Sub lists.