PHPMailer cannot verify that the email server passes

PHPMailer could not verify that the mail server changed the mail server through the company, it was originally using U-MAIL. Now we use Microsoft's exchange. As a result, the original php script fails to connect to the new email server. the prompt is Couldnotauthenticate. How can I diagnose the problem? Note: The script only modifies the connected $ m PHPMailer.
The company changed the mail server, was originally using U-MAIL. Now we use Microsoft's exchange.

As a result, the original php script fails to connect to the new email server, and the prompt is: cocould not authenticate.

How can I diagnose the problem?

Note: The script only modifies the connected $ mail-> Host. Other user names and passwords remain unchanged. In addition, you can use outlook for connection verification. the IP address, user name, and password of the new mailbox can be used.

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Require SSL?
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Http://www.jiucool.com/phpmailer-php-email/

Compare whether your php has installed openssl, account and password, and whether the ip address and port of the smtp server are ssl.