On 10/25/2024 9:47 AM MDT ecdlguy--- via dovecot dovecot@dovecot.org wrote:

Hi,

I'm trying to block specific MUAs, like e.g. Outlook-App for iOS and Android or Xiaomi Mail / MiMail using a lua script. While implementing this, I noticed that "client_id" is always nil in the lua script or I am doing something wrong. This is part of the postfix config:

A note that this is explicitly not a supported IMAP ID use-case.

Per https://www.rfc-editor.org/rfc/rfc2971.html#section-3:

  Servers MUST NOT deny access to or refuse service for a client
  based on information from the ID command.  Clients MUST NOT refuse
  to operate or limit their operation with a server based on the ID
  response.

Client blocking is much better handled via other mechanisms, that may incorporate ID information as a part of the decision making process but does not make a determinative decision based on that string.

michael