Currently we deliver messages of type='error'. It should only happen if such message is addressed to full JID with available resource, see:

1. https://xmpp.org/rfcs/rfc6121.html#rules-localpart-barejid

• 8.5.2.1. Available or Connected Resources > 8.5.2.1.1. Message

For a message stanza of type "error", the server MUST silently ignore the message.

• 8.5.2.2. No Available or Connected Resources > 8.5.2.2.1. Message

For a message stanza of type "headline" or "error", the server MUST silently ignore the message.

2. https://xmpp.org/rfcs/rfc6121.html#rules-localpart-fulljid

• 8.5.3.1. Resource Matches

For a message stanza, the server MUST deliver the stanza to the resource.

• 8.5.3.2. No Resource Matches > 8.5.3.2.1. Message

For a message stanza of type "error", the server MUST silently ignore the stanza.

Ideally, we should create pre-processor to drop those messages.

consider PubSub exception:

https://xmpp.org/extensions/xep-0060.html#publisher-publish-success

The pubsub service MUST then send one event notification to each entity that meets the criteria for receiving an event notification (typically to each approved subscriber, although there are other contexts in which an entity may receive an event notification as summarized under Notification Triggers). Each stanza generated by a pubsub service SHOULD possess an 'id' attribute with a unique value so that the service can properly track any notification-related errors that may occur (see the Handling Notification-Related Errors section of this document).

https://xmpp.org/extensions/xep-0060.html#impl-bounce

f the XMPP error is of type "auth" (e.g., ) or "wait" (e.g., ), or the error condition is , , or , the pubsub service SHOULD increment a bounce counter for that entity and MAY attempt to resend the event notification after some configurable amount of time. The service MAY terminate the subscription of the entity to that node if the bounce counter has reached some configurable limit.

We can use that to remove inactive subscriptions (users from MIX room)