This is not about yate (yet)... but the (formum) mailserver.
The mail server is names ns.null.ro, but the HELO/EHLO announce is yatebts_web4.localdomain
which uses a local name & _ in the name.. where the hostname (ns.null.ro) should be used.
This will land a lot of your mail in spam folders. (or prevent delivery al together due to the _ in the HELO/EHLO announcement.)