==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.6 maria db
- Deployed with iRedMail Easy or the downloadable installer? downloadable installer
- Linux/BSD distribution name and version: ubuntu 22.04.3 lts
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  mysql
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====
from phpmailer webpage whih work until this morning since 2018 now give this and wont send emails anymore and on webpage give this:

SMTP Error: Could not connect to SMTP host. Connection failed. stream_socket_enable_crypto(): SSL
operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed
-------------------------------------------------------------------------------------------
and this is from maillog:

Jun 14 12:21:19 mail postfix/submission/smtpd[48172]: connect from unknown[10.0.0.13]
Jun 14 12:21:19 mail postfix/submission/smtpd[48172]: SSL_accept error from unknown[10.0.0.13]: -1
Jun 14 12:21:19 mail postfix/submission/smtpd[48172]: warning: TLS library problem: error:0A000418:SSL routines::tlsv1 alert unknown ca:../ssl/record/rec_layer_s3.c:1593:SSL alert number 48:
Jun 14 12:21:19 mail postfix/submission/smtpd[48172]: lost connection after STARTTLS from unknown[10.0.0.13]
Jun 14 12:21:19 mail postfix/submission/smtpd[48172]: disconnect from unknown[10.0.0.13] ehlo=1 starttls=0/1 commands=1/2

----------------------------------------------------------------------------------------------
I hope someone tell me how to proceed.. thanks