This has happened to me with a number of different lists I have compiled. They work the first time, and then are rejected - the "name" of the list is treated as an email address, and if not of such a format, the email is rejected. It's hugely annoying, and reproducible. I tried to get round it by saving a manually created email with all the addresses on the list as a template - but can't find how to pull up the template to use for a new email.

Something as basic as a contact list really ought to work, ought it not?