This link sound very helpful. Please run through each step and double check you have everything set up correctly. https://adamtheautomator.com/hmailserver/ The information mentions outgoing server smtp settings using Port 587 (or port 25) and connection security as 'None'. This maybe causing servers to label emails as junk/spam. Suggest you try Port 587 and Connection Security: STARTTLS Authentication Method: Normal Password. Other useful links: https://www.hmailserver.com/functionality https://www.hmailserver.com/documentation/v5.3/?page=basic_configuration https://www.hmailserver.com/documentation/v5.5/?page=reference_protocolsmtp