Can send email but not receive

i have this to main server:


Tipo   Nombre   Destino / IP   Método   TTL
CNAME   smtp   srv1.xxxx.net   Solo DNS   Automático
CNAME   mail   srv1.xxxx.net   Solo DNS   Automático
CNAME   ftp   srv1.xxxx.net   Solo DNS   Automático
CNAME   cpanel   srv1.xxxx.net   Solo DNS   Automático
A   cloud   78.36.107.76   Redirigido mediante proxy   Automático
A   comparen.net   78.36.107.76   Redirigido mediante proxy   Automático
A   intra   78.36.107.76   Redirigido mediante proxy   Automático
A   kb   78.36.107.76   Redirigido mediante proxy   Automático
A   ns1   78.36.107.76   Solo DNS   Automático
A   ns2   78.36.107.76   Solo DNS   Automático
A   propbx   78.36.107.76   Solo DNS   Automático
A   pve-1   78.36.107.76   Solo DNS   Automático
A   srv1   78.46.107.76   Solo DNS   Automático
A   webmail   78.36.107.76   Solo DNS   Automático
CNAME   www   xxxx.net   Redirigido mediante proxy   Automático
MX   comparen.net   mail.xxxx.net   Prioridad: 10, Solo DNS   Automático

And in client domain (i need send and receive in this):

MX   mail   srv1.xxxx.net   Prioridad: 10, Solo DNS   Automático
A   yyyyy.net   78.36.107.76   Redirigido mediante proxy   Automático
A   mail   78.36.107.76   Solo DNS   Automático
A   www   78.36.107.76   Redirigido mediante proxy   Automático
MX   yyyyy.net   srv1.xxxx.net   Prioridad: 10, Solo DNS   Automático
TXT   yyyyy.net   "v=spf1 mx a ip4:78.36.107.76 ~all"   Solo DNS   Automático


what is the problem?

It looks like there is misconfiguration of the MX records of your domain. Check and make sure they are correct.

Check the MX record using the looks like mxtools:
https://mxtoolbox.com/

in fresh install i need to comment smtpd_client_restrictions = reject_unknown_client
in postfix/main.cfg

If you removed reject_unknown_client from  smtpd_client_restrictions  and it solved the problem then it means the source mail server is misconfigured a bit. Most likely it has a wrong RDNS record or doesn't have it at all.

in fresh install i need to comment smtpd_client_restrictions = reject_unknown_client
in postfix/main.cfg

This is not safe.  You have opened up your mail server to possibly used as a spam server.  You need to find the root issue of the problem.

As cyberspace said, you have no valid rDNS value for the IP https://dnschecker.org/reverse-dns.php?query=78.36.107.76.  YOu need to contact your host to updated your PTR record to your servername.