Error 450 4.7.1 Client host rejected: cannot find your hostname, but PTR record is OK.

Hello people. I'm new to cPanel / WHM but specializing in Linux and servers. I have 4 IP addresses for my server. I needed to make the IP change for one domain only (eg: server01.cwbsistemas.com.br), the others remain with the same IP. I managed to make change by the WHM panel, but now the emails are coming back with the error: host fagundez.domain.com.br [] SMTP error from remote mail server after RCPT TO: : 450 4.7.1 Client host rejected: cannot find your hostname, []: retry timeout exceeded I checked several solutions and the PTR is correct. And the exim settings too. Does anyone have any ideas ? Forgive my English is from automatic translation.