“For security reasons DTD is prohibited in this XML document” error in Veeam Backup for Microsoft 365

KB ID: 2821
Product: Veeam Backup for Microsoft 365 Community Edition
Veeam Backup for Microsoft 365
Published: 2018-12-11
Last Modified: 2022-05-19
Get weekly article updates
By subscribing, you are agreeing to have your personal information managed in accordance with the terms of Veeam's Privacy Notice.

Cheers for trusting us with the spot in your mailbox!

Now you’re less likely to miss what’s been brewing in our knowledge base with this weekly digest

error icon

Oops! Something went wrong.

Please try again later.

Challenge

Interactions with either SharePoint Online or OneDrive for Business within Veeam Backup for Microsoft 365 fail with either of the following errors:
For security reasons DTD is prohibited in this XML document
Identity Client Runtime Library (IDCRL) could not look up the realm information for federated sign-in

Cause

To communicate with SharePoint online Veeam Backup for Microsoft 365 uses Microsoft CSOM library. When the CSOM library receives an authorization request, it attempts to reach msoid.onmicrosoft.com and msoid.<your-organization-domain>.onmicrosoft.com. Most internet service providers cannot resolve those names, and the CSOM library will quietly ignore those sites being unreachable. However, this only works if the library receives an HTTP error code (e.g., 404, 500, 503, etc.).

The error message occurs when an ISP redirects unresolved DNS calls to their DNS helper page, returning a status code 200 OK. When that happens, the library attempts to authenticate through this “helper” page, which fails with the error “For security reasons DTD is prohibited in this XML document.” or “Identity Client Runtime Library (IDCRL) could not look up the realm information for federated sign-in.”

Solution

While the issue is out of Veeam’s support scope, what follows is a list of solutions customers have reported resolved their issue:

Option 1: Contact the ISP

Some customers have reported that they were able to contact their ISP and request that the DNS relay or DNS helper feature be disabled.

 

Option 2: Edit the hosts file

Create entries within the hosts fileC:\Windows\System32\drivers\etc\hosts of the Veeam Backup for Microsoft 365 server to force the msoid domains to resolve to the loopback IP of 127.0.0.1.

hosts file

Option 3: Add a record to domain DNS

Add a CNAME record on your DNS server as shown here:

dns
Click here to send feedback regarding this KB, or suggest content for a new KB.
To report a typo on this page, highlight the typo with your mouse and press CTRL + Enter.

Spelling error in text

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Thank you!

Thank you!

Your feedback has been received and will be reviewed.

Oops! Something went wrong.

Please try again later.

KB Feedback/Suggestion

This form is only for KB Feedback/Suggestions, if you need help with the software open a support case

By submitting, you are agreeing to have your personal information managed in accordance with the terms of Veeam's Privacy Notice.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Verify your email to continue your product download
We've sent a verification code to:
  • Incorrect verification code. Please try again.
An email with a verification code was just sent to
Didn't receive the code? Click to resend in sec
Didn't receive the code? Click to resend
Thank you!

Thank you!

Your feedback has been received and will be reviewed.

error icon

Oops! Something went wrong.

Please try again later.