I have compiled dovecot 2.3.6 on RH 8, and I copied the configuration from dovecot 2.0.9

however, when I try to connect the new machine the certificate is not recognized

The same certificate is working with apache

CONNECTED(00000004)

depth=0 ...

verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 ...
verify error:num=21:unable to verify the first certificate
verify return:1

...

---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 2311 bytes and written 404 bytes
Verification error: unable to verify the first certificate