Have to agree with this. I ran my own mail server for a few years and even though set up was easy, deliverability was a PITA (I was never able to successfully deliver to hotmail addresses even after doing everything possible on my end).
Then there's spam.. what a headache. Suddenly one day I realised that I have better things to do with my time and now everything goes through google servers.
Did you install greylisting and blacklisting? It really do reduce spam to ~0, and is a one time 5-20m configuration.
As for hotmail, I strongly remember doing a telnet to hotmail servers and succeeded in sending emails while writing commands by hand on my private computer. Thus without any special headers or other magic, I could send email without any issues. It would had been interesting to hear details on why hotmail rejected your emails. Default postfix installation?
Then there's spam.. what a headache. Suddenly one day I realised that I have better things to do with my time and now everything goes through google servers.