TeamPass before 3.1.3.1 does not properly check whether a mail_me (aka action_mail) operation is on behalf of an administrator or manager.
https://github.com/nilsteampassnet/TeamPass/compare/3.1.3...3.1.3.1
https://github.com/nilsteampassnet/TeamPass/compare/3.1.2...3.1.3.1
https://github.com/nilsteampassnet/TeamPass/commit/35e2b479f2379545b4132bc30a9d052ba7018bf9