Postfix sends email to spam (gmail, hotmail)
Did you setup reverse DNS properly? Make sure the forward and reverse records for your mail server match.
So, Gmail tells you:
Why is this message in Spam? It's similar to messages that have been detected by our spam filters.
This is generally a problem with spammy looking content.
And indeed, if I received a message containing "ciao bello ti invio il codice la prossima volta fammi sapere" I'd probably mark it as spam too. It's certainly spammy looking enough.
You can do two things:
- Rewrite your content to be more professional in nature.
- Click "Not Spam" a lot.