I already had the mailbox syncs with Creatio for sending emails, so I just added it to the [ List of mailboxes for case registration ] lookup. (like I found in this article:
I would like to suggest you to double-check whether all the further steps (4-11) from the mentioned article have been completed as well.
It should be enough for Creatio to start processing all emails received by the mailboxes in the case registration system.
If all the steps are completed in accordance with the instruction and you still have issues with case registration procedure, please contact us at support@creatio.com and specify the name of the instance where the issue occurs so we will be able to investigate the issue further.