Weird notice after the approval of a portrait image by the moderator

my current (test)setting:
Joomla:  3.10.12
CB:        2.9.3+build.2024.09.10.14.21.57.794f9ce0d

problem behaviour:
1. A certain users uploads a new portrait image which has to be approved by the moderator first
2. the moderators logs in and is able to approve the image
3. the following message (notice) appears on the (moderator) screen



4. If the user logs in (after the approval of the moderator) he sees the uploaded portrait image .... so everything seems to be correct

... In order to find out what the cause of this 'notice'  is i made the following checks:

Check 1: System --> Global Configuration -> Mail Settings (Mailer = PHP Mail) -> Click on the button: 'Send Test Mail' -> the test mail will be successfully sent 
Check 2: Does the user get a confirmation e-mail after the approval of his portrait image by the moderator -> Yes, he does
Check 3: Does the moderator also get such a 'weird' notice if he updates his own portrait image? (an approval is not necessary in this case) -> No, he does not (this is correct)

Remark:
- I have seen in the forum that there was also another Joomlapolis-user who described this 'notice' but the context was not the same as mine, so this didn't help me
- This 'issue' (notice) only appears in my test installation (which is based on newer versions). My current productive website (which is based on older versions) has not this issue

Could you please help me?

Regards

That seams like Joomla's below error message.

So an email is trying to send, but no recipient address is supplied. My best guess is 3rd party extension acting on Joomla user store event since CBs emails are sending fine. I suggest taking a look at any 3rd party System or User plugin types in System > Manage > Plugins as something maybe trying to send an email of some kind. It could also be an auto action if you configured an Email auto action, but maybe didn't complete its configuration, on user store triggers.

.... according to your advise I have:

- disabled ALL the 3rd party stuff which I have found under: Extensions / Manage / Manage ..... (independent of which type the selected extension was)
- I have also uninstalled the CB Auto action plugin
- I have also created a new 'moderator' user to be sure that the existing one is not 'corrupt'

Result: everything had no effect ..... this message above appears again after the approval of the moderator ?!?

.... what can I do now?

Enable debug mode and maximum error reporting then retry to see if any errors output. This is just for the avatar field correct and not other image fields?

You are however on Joomla 3.x so there is unlikely we can do anything about this as your Joomla version isn't receiving Joomla updates anymore and it's probably some goofy issue in Joomla's mailer API. If everything is still working despite the message and it's only visible to moderators then it maybe just worth ignoring it and considering migrating to Joomla 4 at the least when possible.