[new] - Cannot use mail.client-domain.tld part 2

ref: Cannot sent user mail.client-domain.tld - Support and Discussion - CyberPanel Community

i just deploy new cyberpanel (fresh install … using ubuntu)
i try to add email to my mail client and gmail too

hostname: server.sample1.tld
mailhost : server.sample1.tld

check sent from rainloop to ping mxtoolbox all green, and spam score 10/10

after that i try to put sample domain let say … client-dom.tld and check the mail subdomain
after all installation
i try to put the user cred on mail client (windows mail, mailbird, gmail) result: error
server smtp: mail.client-dom.tld
username: user@client-dom.tld
pass: same password

but when i change to:
server smtp: server.sample1.tld
username: user@client-dom.tld
pass: same password
everything is working

You sure you have correct DNS settings?

yes i am… everything is set in normal…

anyone facing this ? and how to solve it