Pleks panelde webmail ve mail ssllerinde sıkıntı yok görünüyor fakat wordpress te 587 portu ile test maili göndermeye çalıştığımda şöyle bir hata alıyorum ( kullandığım plugin ; WP MAİL SMTP ) yardımcı olabilirseniz çok sevinirim. Plekste ücretsiz Lets Encrypt ssl kurulu ve 587 port ayarı mail ayarlarından açık durumda bir sıkıntı yok.

Versions:
WordPress: 5.8.3
WordPress MS: No
PHP: 8.0.14
WP Mail SMTP: 3.2.1

Params:
Mailer: smtp
Constants: No
ErrorInfo: SMTP Error: Could not connect to SMTP host.
Host: webmail.domain.com
Port: 587
SMTPSecure: tls
SMTPAutoTLS: bool(true)
SMTPAuth: bool(true)

Server:
OpenSSL: OpenSSL 1.0.2k 26 Jan 2017

Debug:
Email Source: WP Mail SMTP Mailer: Other SMTP SMTP Error: Could not connect to SMTP host.

SMTP Debug:
2022-01-09 17:26:00 Connection: opening to webmail.domain.com:587, timeout=300, options=array()

2022-01-09 17:26:00 Connection: opened

2022-01-09 17:26:00 SERVER -> CLIENT: 220 localhost.localdomain ESMTP Postfix

2022-01-09 17:26:00 CLIENT -> SERVER: EHLO domain.com

2022-01-09 17:26:00 SERVER -> CLIENT: 250-localhost.localdomain250-PIPELINING250-SIZE 10240000250-ETRN250-STARTTLS250-ENHANCEDSTATUSCODES250-8BITMIME250-DSN250 CHUNKING

2022-01-09 17:26:00 CLIENT -> SERVER: STARTTLS

2022-01-09 17:26:00 SERVER -> CLIENT: 220 2.0.0 Ready to start TLS

2022-01-09 17:26:00 Connection failed. Error #2: stream_socket_enable_crypto(): Peer certificate CN=`domain.com' did not match expected CN=`webmail.domain.com' [/var/www/vhosts/domain.com/httpdocs/wp-includes/PHPMailer/SMTP.php line 468]

SMTP Error: Could not connect to SMTP host.

2022-01-09 17:26:00 CLIENT -> SERVER: QUIT

2022-01-09 17:26:00 SERVER -> CLIENT:

2022-01-09 17:26:00 SMTP ERROR: QUIT command failed:

2022-01-09 17:26:00 Connection: closed

SMTP Error: Could not connect to SMTP host.