SMTP Error WordPress

Hi guys,

I’ve some issues with sending E-Mails using SMTP in WordPress. I get the following error:

Versions:
WordPress: 6.4.3
WordPress MS: No
PHP: 7.4.33
WP Mail SMTP: 3.11.1

Params:
Mailer: smtp
Constants: No
ErrorInfo: SMTP Error: Could not authenticate.
Host: web67.alfahosting-server.de
Port: 587
SMTPSecure: tls
SMTPAutoTLS: bool(true)
SMTPAuth: bool(true)

Server:
OpenSSL: OpenSSL 1.0.2k 26 Jan 2017

Debug:
E-Mail-Quelle WP Mail SMTP
Mailer: Anderer SMTP-Server
SMTP Error: Could not authenticate.

SMTP Debug:
2024-02-25 09:09:03 Connection: opening to web67.alfahosting-server.de:587, timeout=300, options=array()

2024-02-25 09:09:03 Connection: opened

2024-02-25 09:09:03 SERVER -> CLIENT: 220 web67.alfahosting-server.de ESMTP Postfix

2024-02-25 09:09:03 CLIENT -> SERVER: EHLO www.triopsgalaxy.de

2024-02-25 09:09:03 SERVER -> CLIENT: 250-web67.alfahosting-server.de250-PIPELINING250-SIZE 104857600250-ETRN250-STARTTLS250-ENHANCEDSTATUSCODES250-8BITMIME250 DSN

2024-02-25 09:09:03 CLIENT -> SERVER: STARTTLS

2024-02-25 09:09:03 SERVER -> CLIENT: 220 2.0.0 Ready to start TLS

2024-02-25 09:09:03 CLIENT -> SERVER: EHLO www.triopsgalaxy.de

2024-02-25 09:09:03 SERVER -> CLIENT: 250-web67.alfahosting-server.de250-PIPELINING250-SIZE 104857600250-ETRN250-AUTH PLAIN LOGIN250-ENHANCEDSTATUSCODES250-8BITMIME250 DSN

2024-02-25 09:09:03 CLIENT -> SERVER: AUTH LOGIN

2024-02-25 09:09:03 SERVER -> CLIENT: 334 VXNlcm5hbWU6

2024-02-25 09:09:03 CLIENT -> SERVER: [credentials hidden]

2024-02-25 09:09:03 SERVER -> CLIENT: 334 UGFzc3dvcmQ6

2024-02-25 09:09:03 CLIENT -> SERVER: [credentials hidden]

2024-02-25 09:09:03 SERVER -> CLIENT: 535 5.7.8 Error: authentication failed: authentication failure

2024-02-25 09:09:03 SMTP ERROR: Password command failed: 535 5.7.8 Error: authentication failed: authentication failure

SMTP Error: Could not authenticate.

2024-02-25 09:09:03 CLIENT -> SERVER: QUIT

2024-02-25 09:09:03 SERVER -> CLIENT: 221 2.0.0 Bye

2024-02-25 09:09:03 Connection: closed

SMTP Error: Could not authenticate.

Can anybody give me some advice so I can take further steps to solve the problem. Thank you!