Hi,
This happened to me once. Emails were not in the respective inbox though the delivery status says 'SENT'. I have then white listed the domain and it worked.
- Go to Administration > Campaign Management Non Deliverables Management > Mail rule sets > Domain Management
- Add your domain (xyz.com/gmail.com) and ask Adobe support team to restart the MTA to finish the whitelisting process.
- You should then be receiving the emails in the inbox.
Please let me know, if this worked.