I have a LAMP server with Ubuntu and Office365 email account.
I need to send email from a PHP page through my Office365 account and I would like to know how to set up my server to enable PHP to send email with a secure connection
There is no custom setup required beyond a standard LAMP server. You can use PHPMailer to send messages via your office365 account.
Once you have PHPMailer you can use code like what's shown below to send your messages:
$mail = new PHPMailer(true);
$mail->Host = "smtp.office365.com";
$mail->Port = 587;
$mail->SMTPSecure = '';
$mail->SMTPAuth = true;
$mail->Username = "email";
$mail->Password = "password";
$mail->SetFrom('email', 'Name');
$mail->addReplyTo('email', 'Name');
$mail->SMTPDebug = 2;
$mail->IsHTML(true);
$mail->MsgHTML($message);
$mail->Send();