Can send email but not receive

[KatiaSisHost]

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?

[cyberspace]

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/

[KatiaSisHost]

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

[cyberspace]

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.

[rcschaff]

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.