Requested action not taken: mailbox unavailable NDR When You Send E-Mail Outside Exchange
Topic Last Modified: 2009-03-19
This topic describes how to troubleshoot a non-delivery report (NDR) message that occurs when you try to send an e-mail message to an e-mail address that includes a special character. For example, the address may include an apostrophe (').
When you try to send an e-mail message to a recipient outside a Microsoft Exchange organization, and the e-mail address includes a special character, you may receive the following NDR message:
Requested action not taken: mailbox unavailable.
To resolve this issue, do not include the special character in the e-mail address.