Relay access denied

I have a domain that has this error, I checked the settings dns, bind, access

The error that the other server returned was:

554 5.7.1 <xxxxx@xxxxxxx.it>: Relay access denied

I'm sorry it's true, is that this morning I'm going crazy with the various domains that have problems.

then I try to send an email from gmail to a domain and I get that error, other domains are working properly.

please tell me which data can be useful to understand the problem. else if redirecting mail from one server to another I have to make some changes over the file postfix / * / domains?