Dear Odhiambo,
The <> represents the "null sender" in SMTP parlance. I think the issue here is that the destination SMTP server does NOT accept the null sender (<>), and that is a br0ken configuration. It has nothing to do with Dovecot though. I am not good at interpreting postfix logs so I cannot advise further.
100% correct answer. I checked with the admin of the relay and it´s working now. Thank you very much Best regards, Wolfgang Burger
