Shared Let's Encrypt ssl error on mail

Hi, please need some suggesttions/help.

On Directadmin/Centos7 server, i've installed the shared Let's Encrypt ssl for admin login and as mail certificate.
After any automated renew, on any Apple devices (using "Mail" program or app) and sometimes "Thunderbird" or any other Client under Windows, certificate is not recognised.
On Thunderbird it's not a really problem (just need accept certificate again) but under Apple devices need reinstall of the mail.

Thanks

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