We have configured the email relay in Office 365 and Salesforce and verified with "Test Deliverability" in Setup successfully by receiving different emails for 10 IP address of salesforce.

But when we sent an email from salesforce to our client, we received a copy of that sent email into our Office365 inbox (instead of in sent item) but our client (using 1client23xxxx@gmail.com email ID) didn't receive that email. Is there anything that we miss. We have used all the domain name like *.salesforce.com etc. instead of IP address. 

Need solution...

1. Sent email in the Sent box folder of O365

2. Client needs to receive the email.