Exchange 2007 550 5.7.1 Message rejected


I have an internal user sending his email via our Exchange 2007, but this email was bounced back due to the content restriction.
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.

The following organization rejected your message:

Diagnostic information for administrators:

Generating server: #< #5.7.1 smtp; 550 5.7.1 Message rejected due to content restrictions> #SMTP#

We are using filtering service from Mailguard. Was this email rejected by our mail filtering system or recipient's email server?
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1. Your user send email to external email address at
2. Generating server:, is this server belong to you?

if no.1 = yes, if no.2 = no, then external recipient reject your email
EducadAuthor Commented:
The belong to us. We use mailguard to filter emails before it arrives to Exchange server. Does that mean mailguard rejected the email?
Minecraft_ EndermanCommented:
Try to disable the mailguard for a test.

Meanwhile, check the content filter on server.
No, the server in questions replying the status code is as this line shows it:

The following organization rejected your message:

but also this line says it: #< #5.7.1 smtp; 550 5.7.1 Message rejected due to content restrictions>

The admin at has to solve this (if willing, to put you on a white list or something, or at least tell you what content in your mail triggered it, so you can fix it, like attachment, wording etc).

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Hello WorldCommented:
According to error message, it rejected because of security policy. Do you have set any security policy in your environment.
You can use message tracking log or protocol log to monitor the deliever process, it's helpful for further troubleshooting.
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