We just had a library reporting that a cart email was denied by a mail server because of the attachement. I think in the current situation we can expect mail servers to get even more critical. I propose that we make sending the attachement optional, maybe with a checkbox on the send cart/list form to avoid these problems. The checkbox could then be hidden with CSS for libraries that experience more problems with this. Alternatively we could also discuss generally removing the attachemeht, as we also offer the option to download in MARC format or a system preference to select the default behaviour.
*** This bug has been marked as a duplicate of bug 2172 ***