error when a have send to gmail ?

useradmin

am using sever mailler this is error, how to fix it ?

aaPanel_Kern

Hello, please check the logs in the mail server to check what is causing the problem.
Check the mail score and troubleshoot according to its error message
https://www.mail-tester.com/

Check blacklists
https://mxtoolbox.com/

Sending to gmail needs to configure SSL, do DKIM, SPF, it is best to let the network provider make the PTR RDNS record of ip

useradmin