09.04.03
[Exim] SMTP protocol violation: synchronization error
This has to be one very annoying message introduced to minimize spam attacks or other hacks. This check (in accordance with the SMTP protocol) was added in exim4. A paper on the exploits is available at:
http://www.remote.org/jochen/sec/hfpa/hfpa.pdf
It turns out that my firewall was also causing problems since i disabled ident. Mailers send back and ident to verify the sender!