We migrated to Office365 earlier in the year. Our website runs on XAMPP and implements sendmail.exe tool in the PHP code to send out notifications to an Office365 mailbox. The PHP and sendmail configs are set correctly (see below). I know because I set it up and tested, and email sending was fine until this week. My question is: How can I check if Office365 is blocking the server? Do I need a separate connector to accept mail? I know that the XAMPP server IP is not listed in spamhaus, I checked. So it's not a delisting issue.
On the server this is the error that I get: "SMTP Error! Could not connect to SMTP host."
Thanks!