Proper "thank yous" for recommendations

[lostmama]

Thanks for your input! We had a late start and just recently completed the recommendation process. My daughter and those who recommended her did all communication with each other via email. We do not have mailing addresses for everyone. In my previous experience, the proper way to thank someone is with a handwritten note. In this instance, is it better to request mailing addresses from those that we do not have in order to send a handwritten note, or to send a thoughtful message of appreciation through email? She has briefly thanked everyone in response to their emails, but I believe we should do more. Thoughts? Thanks!