When searching emails by assigned to "My groups", it can be found mails from other Org Units may also show up to result list.
The standard behavior for search by assigned to "my groups" is that:
If you do a search for 'emails' assigned to 'My groups', the system determines all users belonging to these units/this unit and gets the corresponding worklist for each user. The worklist consists of all emails assigned to a user and all emails that could be assigned to a user. Please further check note 1464849 regarding why it is designed as above.
This design has the following impact:
if, for example, you assign user A to org. units 1, 2 and 3 and user B to org. unit 3. If user B does a group search, he will not only get his worklist, but also the worklist from user A i.e. he will also see workitems intended for users in org. units 1 and 2 as well.
=> You've assigned user A to Org1 and Org2, and you've assigned user B to only Org1.
Org assigement detail in T-code: ppoma_crm:
Organization unit: Org1
Organization unit: Org2
=>If user B logon IC WebUI and he does a “my groups” search in inbox, he will also see workitems/mails intended for all users(user c and user A) in Org2 as well.
1. assign each user to 1 org. unit only
Which means you must make sure that you've only assigned each user to only one unique org.unit. For example, you can't assign one user to org 1 then also assign this user to org 2.
Personally, I think this is difficult for user and org.unit management. When you have lots of users and org units, you will forget which users are assigned to which org.units and if the unique org.unit is assigned.
That's also the reason I recommend you to use below solution 2.
2.implement the BEFORE_SEARCH method of BAdi CRM_IC_INBOX_BADI. You can check note 1375170 and follow the instructions mentioned in it.
Please also check wiki page: Inbox search 2 - search by assigned to "org.unit" in inbox of IC WebUI
Related Notes and KBAs：
Note 1464849 Email, Fax, Letter search in Agent Inbox
Note 1375170 Agent Inbox: Performance workitem (Email,Fax,Letter) search
Note 1400838 Agent Inbox: too few workitems found after note 1375170
Note 1404095 Workitem Search by 'Assigned to Me' returns too many results
Note 1836999 Search for e-mails by org. unit returns too many results
Note 1433713 Performance 'Assigned to' parameter in IC Agent Inbox