"550 5.1.3" NDR message when an Exchange Server 2007 user sends an email message to a recipient

A Microsoft Exchange Server 2007 user tries to send an email message to a recipient whose SMTP address resembles "user.@contoso.com" or "user..lastname@contoso.com". In this situation, the email message is not delivered. Additionally, the user receives the following non-delivery report (NDR) message:


Note The user also cannot receive email messages from this kind of of SMTP address.

This problem occurs because the affected SMTP addresses are non-Request for Comment (RFC) compliant.

To resolve this problem, install the following update rollup: After you apply the update, you must add a new entry in the Edgetransport.exe.config file to enable the update on the server. To do this, follow these steps:

1. On the Exchange 2007-based server that is running the Hub Transport role, open Windows Explorer, and then locate the EdgeTransport.exe.config file. The file is located in the Bin subdirectory of the Exchange Server directory. For example, the file is located in C:\Program Files\Microsoft\Exchange Server\Bin.
2. Create a backup copy of the EdgeTransport.exe.config file, and then name the backup copy EdgeTransport.exe.config.old.
3. Open the EdgeTransport.exe.config file, and then add the following line in the <appSettings> section:
   <add key="AcceptAndFixSmtpAddressWithInvalidLocalPart" value="true" />
4. Save the file.
5. Restart the Exchange Transport service.

Notes

• After you apply the update and add the entry in the Edgetransport.exe.config file, the format of the sender address that is non-RFC compliant becomes "user.”@contoso.com. This format change allows you to reply to these email messages.
• This update does not enable you to send a new email message to a non-RFC compliant address. To do this, you need to put the local part of email address in double quotations (such as "user.”@contoso.com). Some mail servers may not recognize that the SMTP address "user.”@contoso.com is user.@contoso.com. In that case, NDR may return.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about RFC, visit the following IETF website: