Office365 SMTP Connection Fails

I am using the plugin to setup office365 as an outgoing mail relay. I can not get the test emails to go through and therefore, the e-commerce functionality, on this site is not operational as a result of lack of emails. Can you please help me out?

The shop is in test mode and not linked to from the main site yet.

The log message is:

Versions:
WordPress: 4.9.4
WordPress MS: No
PHP: 7.0.29
WP Mail SMTP: 1.2.5

Params:
Mailer: smtp
Constants: No
ErrorInfo: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Host: smtp.office365.com
Port: 587
SMTPSecure: tls
SMTPAutoTLS: bool(true)
SMTPAuth: bool(true)

Server:
OpenSSL: Yes
SMTP Debug:
2018-04-04 07:43:48 Connection: opening to smtp.office365.com:587, timeout=300, options=array (
)
2018-04-04 07:43:48 Connection: opened
2018-04-04 07:43:48 SERVER -> CLIENT: 220-vm.xava-clients.ie ESMTP Exim 4.89_1 #1 Wed, 04 Apr 2018 08:43:48 +0100
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
2018-04-04 07:43:48 CLIENT -> SERVER: EHLO obriengd.ie
2018-04-04 07:43:48 SERVER -> CLIENT: 250-vm.xava-clients.ie Hello obriengd.ie [46.22.137.112]
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-AUTH PLAIN LOGIN
250-STARTTLS
250 HELP
2018-04-04 07:43:48 CLIENT -> SERVER: STARTTLS
2018-04-04 07:43:48 SERVER -> CLIENT: 220 TLS go ahead
2018-04-04 07:43:48 SMTP Error: Could not connect to SMTP host.
2018-04-04 07:43:48 CLIENT -> SERVER: QUIT
2018-04-04 07:43:48 SERVER -> CLIENT: 221 vm.xava-clients.ie closing connection
2018-04-04 07:43:48 Connection: closed
2018-04-04 07:43:48 SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Please copy only the content of the error debug message above, identified with an orange left border, into the support forum topic if you experience any issues.

The page I need help with: [log in to see the link]