Versions:
WordPress: 4.9.4
WordPress MS: No
PHP: 5.6.33
WP Mail SMTP: 1.2.5

Params:
Mailer: smtp
Constants: No
ErrorInfo: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Host: smtp-mail.outlook.com
Port: 587
SMTPSecure: tls
SMTPAutoTLS: bool(true)
SMTPAuth: bool(true)

Server:
OpenSSL: Yes
SMTP Debug:
2018-02-07 11:38:21	Connection: opening to smtp-mail.outlook.com:587, timeout=300, options=array ( ) 2018-02-07 11:38:22	Connection: opened 2018-02-07 11:38:22	SERVER -> CLIENT: 220 LNXP265CA0069.outlook.office365.com Microsoft ESMTP MAIL Service ready at Wed, 7 Feb 2018 11:38:21 +0000 2018-02-07 11:38:22	CLIENT -> SERVER: EHLO shishkebabb.com 2018-02-07 11:38:22	SERVER -> CLIENT: 250-LNXP265CA0069.outlook.office365.com Hello [77.104.173.38] 250-SIZE 157286400 250-PIPELINING 250-DSN 250-ENHANCEDSTATUSCODES 250-STARTTLS 250-8BITMIME 250-BINARYMIME 250-CHUNKING 250 SMTPUTF8 2018-02-07 11:38:22	CLIENT -> SERVER: STARTTLS 2018-02-07 11:38:22	SERVER -> CLIENT: 220 2.0.0 SMTP server ready 2018-02-07 11:38:22	CLIENT -> SERVER: EHLO shishkebabb.com 2018-02-07 11:38:22	SERVER -> CLIENT: 250-LNXP265CA0069.outlook.office365.com Hello [77.104.173.38] 250-SIZE 157286400 250-PIPELINING 250-DSN 250-ENHANCEDSTATUSCODES 250-AUTH LOGIN XOAUTH2 250-8BITMIME 250-BINARYMIME 250-CHUNKING 250 SMTPUTF8 2018-02-07 11:38:22	CLIENT -> SERVER: AUTH LOGIN 2018-02-07 11:38:22	SERVER -> CLIENT: 334 VXNlcm5hbWU6 2018-02-07 11:38:22	CLIENT -> SERVER: YmVhbmpvYnNkaWdpdGFsQG91dGxvb2suY29t 2018-02-07 11:38:22	SERVER -> CLIENT: 334 UGFzc3dvcmQ6 2018-02-07 11:38:22	CLIENT -> SERVER: RnJlYWtpc2g3Nzc= 2018-02-07 11:38:28	SERVER -> CLIENT: 535 5.7.3 Authentication unsuccessful [LNXP265CA0069.GBRP265.PROD.OUTLOOK.COM] 2018-02-07 11:38:28	SMTP ERROR: Password command failed: 535 5.7.3 Authentication unsuccessful [LNXP265CA0069.GBRP265.PROD.OUTLOOK.COM] 2018-02-07 11:38:28	SMTP Error: Could not authenticate. 2018-02-07 11:38:28	CLIENT -> SERVER: QUIT 2018-02-07 11:38:28	SERVER -> CLIENT: 221 2.0.0 Service closing transmission channel 2018-02-07 11:38:28	Connection: closed 2018-02-07 11:38:28	SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting