cc field not allow to participant in customer portal

[Silva, Kalpa]

I have created CC multi user field and gave  

Global Permission Browse users and groups to everyone .
But still end users cannot select any users in their portal
and giving me following error.

related   to error "Please provide a valid value for field" (this error fire even valid email is given 

https://confluence.atlassian.com/jirakb/how-to-create-and-configure-cc-participant-field-in-jira-779175047.html

how can i avoid this

[Ivan Tovbin]

In Service desk projects there's already a field for this - 'Request Participants'. The ability of other users to share their requests with other people by adding them to this field is governed by customer permissions on a per project basis.

More info on customer permissions and request participants can be found here and here.

The KB you are referring to relates to Jira Software, not JSD.

[Silva, Kalpa]

is this possible to configure for end clients  too?

[Ivan Tovbin]

Yes. If you give your customers sufficient permissions, they can share their requests with other users on their own.