Working if a configure it to send from a gmail adress with smtp.gmail.com:587 with TLS.

Working if a configure it to send from a gmail adress with smtp.gmail.com:587 with TLS.
Which means that this is obviously a problem with your SMTP provider $g_smtp_host = "ns0.ovh.net"; and not a MantisBT issue

The thing is, when i create a .php which send an email (contains this), it works fine.
But with same settings, mantis don't.

<?php

ini_set("include_path",".:/var/www/mantis/library/phpmailer/");

require("class.phpmailer.php");

$mail = new PHPMailer();

$mail->IsSMTP();
$mail->SMTPAuth = true; // enable SMTP authentication
$mail->Username = "mantis@fgmind.com"; // username
$mail->Password = "Azerty";
$mail->SMTPSecure = "ssl";
$mail->Host = "ssl0.ovh.net"; // sets as the SMTP server
$mail->Port = 465; // set the SMTP port

Still have the badmailfrom error

Does your test script still work if you add the following lines?

$mail->AddCustomHeader('Auto-Submitted:auto-generated');
$mail->AddCustomHeader('X-Auto-Response-Suppress: All');

Yes, works if i add this (even if i don't really understood what it is for).

But i found a solution for this badmailform envelope thing.

I guess mantis or ovh needed a valid mail adress to send all "Delivery failure" messages and stuff like that.

So i added:

$g_return_path_email = 'mantis@noreply.com';

And now it work like a charm.
Maybe this will help someone in future

fgmind,
thanks for coming back and telling the solution.

Does your posted script contain your real connection data for ssl0.ovh.net?
If so, I recommend to change your password.

The difference between your script and MantisBT is, that you did not set return path.
In this case PHPMailer uses the address of the username for the return path.

In MantisBT we set the return path to setting $g_return_path_email
The default value admin@example.com will be used if you don't set it yourself.

It seems that return path admin@example.com is a reason for ns0.ovh.net to deny sending the e-mail but not for smtp.gmail.com.

For the moment it's just a test server, when i'll put it online i'll change password from azerty for sure! :)

I think it could be usefull to document this point, i had to do some researches before finding out the solution. It's not so obvious when you are not very familiar to email protocols and settings.

Something that should be documented and/or checked in admin/check.php?

I don't mind updating the documentation, but considering that this is specific to the SMTP server's settings, I don't think we can/should do something in admin checks.

I don't think we can/should do something in admin checks.

We did already in master
https://github.com/mantisbt/mantisbt/blob/master/admin/check/check_email_inc.php#L51