Certificate not valid

Hi, everyone
I have little problem when make email account and try to sign in from for exmaple android phone it shows me "Certificate not valid" i can continue and its working sending and receive emails but its shows me this message can i fix it?

You must have a valid SSL Certificate installed for the hostname that you are using while sending emails.

if you have a valid A record set for your hostname try also check that you have rDNS set with your server provider and then change hostname from cwp.
By changing hostname from cwp if you have an A record for it you will get letsencrypt (autoSSL) certificate installed automatically.

It would be also recommended to rebuild mail server after that, you can do that also from cwp.

if you have a valid A record set for your hostname try also check that you have rDNS set with your server provider and then change hostname from cwp.
By changing hostname from cwp if you have an A record for it you will get letsencrypt (autoSSL) certificate installed automatically.

It would be also recommended to rebuild mail server after that, you can do that also from cwp.

This topic it's a bit old but I have the same problem everytime my certificate is renewed I get errors on email server and I need to rebuild it. Can we automatize this rebuild?