SMTP connect failed

Can someone help to understand why i’m receiving this error?
thank you

Versions:
WordPress: 4.9.6
WordPress MS: No
PHP: 7.1.14
WP Mail SMTP: 1.2.5

Params:
Mailer: smtp
Constants: No
ErrorInfo: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Host: mail.altanaspa.com
Port: 25
SMTPSecure: string(0) ""
SMTPAutoTLS: bool(false)
SMTPAuth: bool(true)

Server:
OpenSSL: Yes
Apache.mod_security: No
SMTP Debug:
2018-05-18 17:08:24	Connection: opening to mail.altanaspa.com:25, timeout=300, options=array (
)
2018-05-18 17:08:24	Connection: opened
2018-05-18 17:08:29	SERVER -> CLIENT: 220 mail.altanaspa.com ESMTP Service ready
2018-05-18 17:08:29	CLIENT -> SERVER: EHLO www.altanaspa.com
2018-05-18 17:08:29	SERVER -> CLIENT: 250-Requested mail action okay, completed
250-8BITMIME
250-SIZE 30000000
250 OK
2018-05-18 17:08:29	SMTP Error: Could not authenticate.
2018-05-18 17:08:29	CLIENT -> SERVER: QUIT
2018-05-18 17:08:29	SERVER -> CLIENT: 221 Service closing transmission channel
2018-05-18 17:08:29	Connection: closed
2018-05-18 17:08:29	SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

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