SMTP Error

Hi,
I want to set up WP Mail SMTP on a website.
Even if all the information is correct, I get the following error message:

Versions:
WordPress: 6.1.1
WordPress MS: No
PHP: 7.3.33
WP Mail SMTP: 3.6.1

Params:
Mailer: smtp
Constants: No
ErrorInfo: 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 failedSMTP server error: QUIT command failed
Host: mail.test.de
Port: 587
SMTPSecure: tls
SMTPAutoTLS: bool(true)
SMTPAuth: bool(true)

Server:
OpenSSL: OpenSSL 1.1.1k  FIPS 25 Mar 2021

Debug:
E-Mail-Quelle WP Mail SMTP
Mailer: Benutzerdefinierter SMTP-Server
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 failedSMTP server error: QUIT command failed

SMTP Debug:

2022-12-07 16:15:12 Connection: opening to mail.test.de:25, timeout=300, options=array()

2022-12-07 16:15:12 Connection: opened

2022-12-07 16:15:12 SERVER -> CLIENT: 220 SRVEX01.test.de Microsoft ESMTP MAIL Service ready at Wed, 7 Dec 2022 17:15:12 +0100

2022-12-07 16:15:12 CLIENT -> SERVER: EHLO www.test.de

2022-12-07 16:15:12 SERVER -> CLIENT: 250-SRVEX01.test.de Hello [92.204.55.209]250-SIZE 104857600250-PIPELINING250-DSN250-ENHANCEDSTATUSCODES250-STARTTLS250-X-ANONYMOUSTLS250-AUTH NTLM250-X-EXPS GSSAPI NTLM250-8BITMIME250-BINARYMIME250-CHUNKING250-SMTPUTF8250 XRDST

2022-12-07 16:15:12 CLIENT -> SERVER: STARTTLS

2022-12-07 16:15:12 SERVER -> CLIENT: 220 2.0.0 SMTP server ready

2022-12-07 16:15:12 Connection failed. Error #2: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed [/kunden/502316_31177/webseiten/wp-includes/PHPMailer/SMTP.php line 468]

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

2022-12-07 16:15:12 CLIENT -> SERVER: QUIT

2022-12-07 16:15:12 SERVER -> CLIENT: 

2022-12-07 16:15:12 SMTP ERROR: QUIT command failed: 

2022-12-07 16:15:12 Connection: closed

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

I have already tried different ports for TSL. Another developer said that the CA list must be renewed in wordpress. Is that possible at all? I have never heard anything about it.