userIDListindicates your own UserID.
By default, the IM SDK does not check the relationship between two parties when sending one-to-one chat messages. This default setting is generally applied in customer service scenarios, where having to friend a customer service agent before chatting is inefficient.
If you want to demand users to be friends before they can chat, log in to the IM console, choose Feature Configuration > Login and Message > Relationship Check, and enable Check Relationship for One-to-One Messages. With this feature enabled, users can send messages to friends only, and will receive the 20009 error code from the SDK when sending a message to a non-friend user.
By default, the IM SDK does not prevent message sending and receiving between strangers. If you want messages to be sent or received only between friends, log in to the IM console, choose Feature Configuration > Login and Messages > Relationship Check, and enable Check Relationship for One-to-One Messages. After this feature is enabled, you can send messages only to friends. When you try to send messages to strangers, the IM SDK returns the 20009 error code.
When a user is added to the blocklist, by default, the user does not know that he/she is in the blocklist. That is, after this user sends a message, the user is still prompted that the message was sent successfully, but in fact, the recipient will not receive the message. If you want a user in the blocklist to know that his/her message failed to be sent, log in to the IM console, choose Feature Configuration > Login and Message > Blocklist Check, and disable Show "Sent successfully" After Sending Messages. After this feature is disabled, the IM SDK will return the 20007 error code when a user in the blocklist sends a message.
There are two types of user profile updates in the enhanced SDK: