Since the email function of the Directory uses your computer's email client, I don't see how this suggestion could be implemented. It's your email client that is sending the message, so that's the application that would have to break up the recipient list into multiple chunks. No LDS.org application is involved in sending the message.
And I think when you say "the message is truncated" you really mean that the recipient list is truncated. Correct?
[Moderator note: I moved this post here from the
"All" Category thread in the Beta Newsletter forum, since it deals with the Directory, not the Newsletter.]
Questions that can benefit the larger community should be asked in a public forum, not a private message.