Default mailbox can't receive any mail, but can send

Hello, I'm configuring a new WHM - CPanel for a client, and I'm experencing an issue with the incoming mail for all default mailbox of all domains. Here the symptoms : 1) I go in the CPanel of the domain, and Goto mailbox. I click on the default malbox of the domain, and use Roundcube Webmail 1.4.6 a mail client. I can send mail, and receive it from de destination mail. 2) In the destimation mail, I click replay to, and send a response. I dont see the response in the default mailbox. 3) in the exim_mainlog (tail -f /var/log/exim_mainlog), the response is that : 2020-08-21 06:33:00 remote host address is the local host: server.mydomain.com (while verifying from host mail-pj1-f54.google.com [209.85.216.54]:54392) 2020-08-21 06:33:00 H=mail-pj1-f54.google.com [209.85.216.54]:54392 X=TLS1.2:ECDHE-RSA-AES128-GCM-SHA256:128 CV=no F= temporarily rejected RCPT : remote host address is the local host 2020-08-21 06:33:00 SMTP connection from mail-pj1-f54.google.com [209.85.216.54]:54392 closed by QUIT Take note : server.mydomain.com, samplemail@sample.com and customdomain are remplaced to hide real information. 4) I have remarked that other mailbox I create work really well. If the mailbox is not by default, I can send and receive mails. Anyone have an idea for what reason the default mailbox can't receive any mail ?