Sergiy:Yes, I have this, although you mentioning this answered the question for me. I added the following configuration item to the mail server smtpaccess.
10.64.1.10 AUTH_REQUIRED=0,BOFHNOVRFY=1,allow,relayclientBOFHNOVRFY tells submit not to check if the address is local. This solved my problem. Hope this helps someone in the future.
Thanks HFC
Did you allow relaying for your sendmail boxes on your courier mta box ? There's a courier access file which you can use for that, e.g. 10 allow,RELAYCLIENT
smime.p7s
Description: S/MIME Cryptographic Signature
