Email Bounced?

[sheepy]

Hey there.
I've been having some trouble with emails being bounced from phpbb3 boards.
Some people have an option to be notified by email that they have a pm.
Also my board sends a welcome message when people first register.
But I keep emails like this sent to me.

1222255985
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

f.loupatty@home.nl
does not like recipient.
Remote host said: 550 This address does not receive mail. Invalid delivery.

------ This is a copy of the message, including all the headers. ------

Return-path: <bounce+sheepy@theory-guild.co.uk>
Received: from [86.160.86.236]
by unlimitedmb.com with HTTP
for f.loupatty@home.nl
Wed, 24 Sep 2008 11:33:04 +0000
X-Anti-Abuse: This tag has been added to track the source of this message.
X-Anti-Abuse: Please include it in any abuse report.
X-Anti-Abuse: This email has been sent using PHP by our web hosting customer.
X-Anti-Abuse: We do not allow our servers to be used to send spam.
X-Anti-Abuse: Send abuse reports to abuse@unlimitedmb.com
X-Anti-Abuse: Message sent from account [theory-guild.co.uk]
X-Anti-Abuse: Script Path [/hosted/domains/t/h/theory-guild.co.uk/public_html/forums/cron.php]
X-Anti-Abuse: Sent To: f.loupatty@home.nl (f dot loupatty at home dot nl)
Precedence: junk
To: "=?UTF-8?B?QnNhZnJhbmt5?=" <f.loupatty@home.nl>
Subject: =?UTF-8?B?TmV3IHByaXZhdGUgbWVzc2FnZSBoYXMgYXJyaXZlZA==?=
From: <sheepy@theory-guild.co.uk>
Reply-To: <sheepy@theory-guild.co.uk>
Return-Path: <sheepy@theory-guild.co.uk>
Sender: <sheepy@theory-guild.co.uk>
MIME-Version: 1.0
Message-ID: <ce153bff9d025fb0e531f0f26b55bb95@http://www.theory-guild.co.uk>
Date: Wed, 24 Sep 2008 11:33:02 +0000
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: PhpBB3
X-MimeOLE: phpBB3
X-phpBB-Origin: phpbb://www.theory-guild.co.uk/forums

Hello Bsafranky,

You have received a new private message from "Dagda" to your account on
"Theory" with the following subject:

totemrage

You can view your new message by clicking on the following link:

http://www.theory-guild.co.uk/forums/ucp.php?i=pm&folder=inbox

You have requested that you be notified on this event, remember that you
can always choose not to be notified of new messages by changing the
appropriate setting in your profile.

--
Thanks,
Admin from Theory

Can someone tell me why this is?
Thanks in advanced

[UnlimitedMB]

The email address f.loupatty@home.nl is invalid.

[sheepy]

ok. TY for that info.
Does this mean whenever I recieve this mail its because the email address is invalid?

[UnlimitedMB]

Yes its because someone signed up to your forum with an email that does not exist anymore.

We intend to block bounces for php auto generated mail in future, but its not done yet.

[sheepy]

OK ty for your help an time :)