Froxlor through 2.3.10 does not enforce the mail.allow_external_domains policy in the EmailSender.add API command. When an administrator has enabled the allowed-sender feature but disabled external a…

Summary

Froxlor through 2.3.10 does not enforce the mail.allow_external_domains policy in the EmailSender.add API command. When an administrator has enabled the allowed-sender feature but disabled external allowed-sender domains (mail.enable_allow_sender = 1, mail.allow_external_domains = 0), an authenticated customer with API access can still use EmailSender.add to register an arbitrary external sender address for their mailbox, which is stored despite the policy. This creates a bypass between the UI/…