local server using 587 port (starttls)

10:42:34/210602(~)% foreach i (587)
echo $i;  openssl x509 -text -noout -in <(openssl s_client  -connect imap.example.com:$i -starttls smtp) |& grep -A3 Validity
end
587
depth=1 C = US, O = Let's Encrypt, CN = R3
verify return:1
depth=0 CN = imap.example.com
verify return:1
250 HELP
DONE
        Validity
            Not Before: Mar 12 11:22:45 2021 GMT
            Not After : Jun 10 11:22:45 2021 GMT
        Subject: CN = imap.example.com

Office server

10:48:01/210602(~)% foreach i (465  993 995)
echo $i;  openssl x509 -text -noout -in <(openssl s_client  -connect mail.domain.example.com:$i ) |& grep -A3 Validity
end
465
depth=1 C = US, O = Let's Encrypt, CN = R3
verify return:1
depth=0 CN = domain.example.com
verify return:1
DONE
        Validity
            Not Before: Mar 12 07:10:42 2021 GMT
            Not After : Jun 10 07:10:42 2021 GMT
        Subject: CN = domain.example.com
993
depth=1 C = US, O = Let's Encrypt, CN = R3
verify return:1
depth=0 CN = domain.example.com
verify return:1
DONE
        Validity
            Not Before: Mar 12 07:10:42 2021 GMT
            Not After : Jun 10 07:10:42 2021 GMT
        Subject: CN = domain.example.com
995
depth=1 C = US, O = Let's Encrypt, CN = R3
verify return:1
depth=0 CN = domain.example.com
verify return:1
DONE
        Validity
            Not Before: Mar 12 07:10:42 2021 GMT
            Not After : Jun 10 07:10:42 2021 GMT
        Subject: CN = domain.example.com