With spam and viruses distributed via email, it would seem to me that getting 65+ k folks to click on attachments is counter productive; so is storing 65+ k copies on customers' servers and/or local storage.
Distributing a URL of an official web site would seem useful, especially if the attachment gets updated or revised.
I can not recall the last time I had an attachment distributed via a LISTSERV(R) list, and have explicited discarded them on lists that I co-operate[d].
When the need arose for a file to be distributed, instead we stored it on a server and referenced the URL.
/Pete